MQL4: How Can You Change the Magic Number of an Order?

Expert Advisors (EAs) operating within the MetaTrader environment often manage multiple trading positions simultaneously. These positions might stem from different trading strategies, different instances of the same strategy, or even strategies running on the same account but originating from different charts or symbols. Distinguishing ownership and intent for each order is crucial for proper management, and this is where the ‘Magic Number’ plays a vital role.

What is a Magic Number?

The Magic Number is an integer value assigned to an order when it is opened using functions like OrderSend() in MQL4 (or OrderSend() / OrderSendAsync() in MQL5). It is a custom identifier chosen by the programmer to uniquely mark orders placed by a specific Expert Advisor, strategy, or even a particular instance of a strategy on a chart. Its value is an integer, typically ranging from 0 to INT_MAX, although certain ranges or specific values might be reserved by MetaTrader or brokers for internal use (e.g., manual orders often have a magic number of 0 or another default).

Why are Magic Numbers Important?

For an EA to effectively manage its own open positions and pending orders without interfering with trades placed manually by the user, by other EAs running on the same terminal, or even by different strategies within the same EA, it needs a reliable method to identify its trades. The Magic Number provides this isolation. When iterating through the terminal’s pool of orders (using OrdersTotal() and OrderSelect()), an EA checks the OrderMagicNumber() property of each order. If the retrieved magic number matches the one assigned to the EA, it considers the order as its own and proceeds with management logic (e.g., modifying stop losses, checking for closure conditions, etc.). Without magic numbers, managing trades becomes chaotic and prone to errors, especially in scenarios involving multiple EAs or manual trading on the same account.

Common Use Cases for Magic Numbers

• Multiple EAs on One Account: Each EA uses a unique magic number to manage its own trades independently.
• Multiple Strategies within One EA: A single EA implementing several strategies assigns a different magic number to orders opened by each strategy.
• Managing Orders from Specific Charts/Symbols: While less common as Symbol is usually checked, a magic number could incorporate chart or symbol information if needed for complex multi-symbol strategies.
• Distinguishing Manual vs. Automated Trades: EAs are typically configured to ignore orders with a magic number of 0 (often used for manual trades).

Understanding Order Modification in MQL4

Managing open positions often requires adjusting parameters like Stop Loss (SL), Take Profit (TP), or Expiration times for pending orders. MQL4 provides a dedicated function for this purpose: OrderModify().

The OrderModify() Function

The OrderModify() function is used to change the parameters of an existing open position or pending order. Its successful execution is critical for dynamic strategy adjustments, such as trailing stops or time-based order cancellations.

The function signature is:

bool OrderModify(
   int    ticket,
   double price,
   double stoploss,
   double takeprofit,
   datetime expiration,
   color  arrow_color
);

Let’s briefly look at the parameters:

• ticket: The unique identifier (ticket number) of the order to be modified. This is obtained by selecting the order (e.g., using OrderSelect() and then OrderTicket()).
• price: For pending orders (Buy Limit, Sell Limit, Buy Stop, Sell Stop), this is the new price level. For market orders (Buy, Sell), this parameter is ignored and usually passed as 0.
• stoploss: The new Stop Loss price level. Use 0 to remove the Stop Loss.
• takeprofit: The new Take Profit price level. Use 0 to remove the Take Profit.
• expiration: The new expiration time for pending orders. Use 0 for no expiration. For market orders, this parameter is ignored.
• arrow_color: The color of the arrow that appears on the chart indicating the modification point. Can be CLR_NONE for no arrow.

The function returns true if the modification request was successfully sent to the server, and false otherwise. Errors can be retrieved using GetLastError().

Parameters of OrderModify() relevant to Magic Number changes

Crucially, looking at the parameters of OrderModify() listed above, one thing is immediately apparent: The Magic Number is NOT a parameter of the OrderModify() function.

Limitations and Considerations

This is the fundamental limitation regarding changing the Magic Number of an order in MQL4 (and MQL5): You cannot change the Magic Number of an order after it has been successfully opened (or placed, for pending orders) using the OrderModify() function or any other standard MQL4 order management function. The Magic Number is set only at the time the order is sent using OrderSend().

If the need arises to assign a ‘new’ identifier to an existing position based on some changed condition, the common approach is not to modify the magic number (as it’s impossible) but rather to:

1. Close the existing position (using OrderClose()).
2. Open a new position with the desired new Magic Number and potentially other updated parameters.

However, this approach incurs additional spread/commission costs and potential slippage, making it impractical for simple identifier changes.

It is highly likely that a developer asking how to change the magic number might be confusing it with the order’s comment (OrderComment()), which can be changed in MQL5 using the PositionComment() function within PositionModify() (though not directly in MQL4 for open orders). The Magic Number, however, is a permanent attribute of an order once placed.

Changing the Magic Number: Step-by-Step Guide

As established, you cannot change the magic number of an existing order in MQL4. However, you can and must identify orders by their magic number before attempting to modify other parameters like SL or TP using OrderModify(). This section will outline the process of selecting an order based on its magic number and then modifying its valid parameters.

Identifying the Order to Modify

Before calling OrderModify(), you need the ticket number of the specific order you want to modify. This involves iterating through the pool of orders currently managed by the terminal and filtering them based on criteria, including the magic number. The steps are:

1. Get the total number of orders and positions using OrdersTotal().
2. Loop from OrdersTotal() - 1 down to 0 (looping downwards is safer if you might be closing orders during the loop, though not relevant for modification).
3. Inside the loop, select each order using OrderSelect(index, SELECT_BY_POS, MODE_TRADES).
4. Check if the selected order meets your criteria: OrderMagicNumber() == YourMagicNumber, OrderSymbol() == Symbol(), OrderType() is appropriate (e.g., OP_BUY or OP_SELL), etc.
5. If the order matches, retrieve its ticket number using OrderTicket(). This is the ticket you will pass to OrderModify().

Implementing the OrderModify() Function with the New Magic Number

This heading is still misleading given the restriction. Let’s rephrase the intent: Implementing the OrderModify() function on an order identified by its Magic Number. Once you have identified the order’s ticket using the steps above, you can call OrderModify() to change its SL, TP, expiration, or pending price.

You cannot provide a new Magic Number to OrderModify(). The function doesn’t accept it as a parameter. You use OrderModify() because you have already identified an order with a specific, existing Magic Number that you want to manage.

The call will look like this, assuming you have the order’s ticket and your desired new stoploss, takeprofit, etc.:

bool success = OrderModify(ticket, 0, new_stoploss, new_takeprofit, 0, CLR_NONE);

(Note: price and expiration are set to 0 here, assuming a market order where they are ignored or not needed for modification. Adjust these for pending orders).

Example Code Snippet: Changing Magic Number

This heading is inherently incorrect as the Magic Number cannot be changed. A correct example will show how to find an order by Magic Number and then modify its SL/TP.

//--- Define your EA's magic number
#define MY_MAGIC_NUMBER 12345

//--- Function to modify the Stop Loss and Take Profit of an order
//--- identified by its ticket and confirming its magic number
bool ModifyOrderByTicketAndMagic(
   int    order_ticket,
   int    expected_magic,
   double new_stoploss,
   double new_takeprofit
) {
   // Select the order by ticket
   if (!OrderSelect(order_ticket, SELECT_BY_TICKET)) {
      Print("Error selecting order ticket ", order_ticket, ": ", GetLastError());
      return(false);
   }

   // Verify the magic number to ensure this is our order
   if (OrderMagicNumber() != expected_magic) {
      Print("Error: Order ticket ", order_ticket, " has incorrect magic number (", OrderMagicNumber(), ") - Expected ", expected_magic);
      return(false);
   }

   // Verify symbol and type (optional but good practice)
   if (OrderSymbol() != Symbol() || (OrderType() != OP_BUY && OrderType() != OP_SELL)) {
       Print("Order ticket ", order_ticket, " is not for this symbol or is a pending order. Modification skipped.");
       // Adjust logic if you intend to modify pending orders
       return(false);
   }

   // Get current SL/TP
   double current_sl = OrderStopLoss();
   double current_tp = OrderTakeProfit();

   // Check if modification is actually needed to avoid unnecessary calls
   // Need to account for potential floating point inaccuracies
   if (MathAbs(new_stoploss - current_sl) < MarketInfo(Symbol(), MODE_POINT) * 10 &&
       MathAbs(new_takeprofit - current_tp) < MarketInfo(Symbol(), MODE_POINT) * 10) {
      Print("Order ticket ", order_ticket, ": SL/TP already at target levels. No modification needed.");
      return(true); // Consider it successful as desired state is met
   }

   // Perform the modification (price=0, expiration=0 for market orders)
   bool modify_result = OrderModify(
      order_ticket,      // Order ticket
      0,                 // Price (ignored for market orders)
      new_stoploss,      // New Stop Loss
      new_takeprofit,    // New Take Profit
      0,                 // Expiration (ignored for market orders)
      CLR_NONE           // Arrow color
   );

   // Check the result of the modification attempt
   if (modify_result) {
      Print("Successfully sent modification request for ticket ", order_ticket);
      // Note: Success of the request doesn't guarantee server execution. 
      // You should re-check order state after a delay.
   } else {
      Print("Failed to send modification request for ticket ", order_ticket, ": ", GetLastError());
   }

   return(modify_result);
}

//--- Example usage within an EA tick function or similar logic
void OnTick() {
   // ... (your trading logic to identify *which* order to modify)

   int order_to_modify_ticket = -1; // Assume you found the ticket earlier
   double desired_sl = 1.1200;
   double desired_tp = 1.1500;

   // Example of finding a specific order by magic number and symbol first
   for (int i = OrdersTotal() - 1; i >= 0; i--) {
      if (OrderSelect(i, SELECT_BY_POS, MODE_TRADES)) {
         if (OrderMagicNumber() == MY_MAGIC_NUMBER && OrderSymbol() == Symbol()) {
            // Found an order belonging to this EA on this symbol
            order_to_modify_ticket = OrderTicket();
            // In a real EA, you might have more complex logic to pick *which* order
            // For this example, let's just take the first one found.
            break;
         }
      }
   }

   if (order_to_modify_ticket != -1) {
      // Now modify its SL/TP using the function
      ModifyOrderByTicketAndMagic(order_to_modify_ticket, MY_MAGIC_NUMBER, desired_sl, desired_tp);
   }
   // ... (rest of your OnTick logic)
}

The key takeaway is that the provided code demonstrates finding an order based on its existing Magic Number and then using OrderModify() to change other parameters. It does not, and cannot, change the Magic Number itself.

Practical Examples and Use Cases

While you cannot change the magic number of an open order, understanding this limitation is crucial for implementing robust trading strategies. Practical scenarios involve selecting orders by their magic number before executing modification logic.

Changing Magic Numbers Based on Strategy Type

As previously noted, if you run multiple strategies within a single EA, you’d assign a distinct magic number to orders opened by each strategy. When your EA needs to manage orders (e.g., adjust stops), it iterates through OrdersTotal(), checks OrderMagicNumber(), and applies the appropriate modification logic specific to the strategy associated with that magic number. You don’t change the magic number; you use it as a filter to apply the correct OrderModify() parameters or logic.

Modifying Magic Numbers During Order Updates

The phrase “Modifying Magic Numbers During Order Updates” is also misleading. You are not modifying the magic number. You are updating the order’s parameters (SL, TP, etc.) while using the order’s existing magic number as part of the criteria to select which orders to update. For example, a trailing stop logic would iterate through all open orders, check if OrderMagicNumber() matches the EA’s number, and if the order is a Buy or Sell position. If it is, the EA calculates the new trailing stop level and calls OrderModify() with the order’s ticket and the calculated stop loss. The magic number is used for identification, not modification.

Best Practices and Troubleshooting

Working with order modification and magic numbers requires adherence to best practices to ensure your EA behaves correctly and manages trades reliably.

Error Handling When Modifying Orders

Always check the return value of OrderModify(). If it returns false, call GetLastError() to understand the reason for failure. Common errors include invalid parameters (ERR_INVALID_PARAMETERS), trade being disabled (ERR_TRADE_DISABLED), or server-side rejections (e.g., stop loss too close to current price – ERR_INVALID_STOPS). Proper error handling allows you to log issues or retry modifications if appropriate.

Avoiding Conflicts with Other Expert Advisors

The primary purpose of magic numbers is conflict avoidance. Ensure every EA you run on the same account (or even different strategies within one EA) uses a unique magic number. This prevents an EA from accidentally trying to manage or close orders placed by another EA or manual trades. When iterating through orders, always filter not just by symbol and type but critically by OrderMagicNumber() matching your EA’s assigned number.

Ensuring Order Modification Success

Even if OrderModify() returns true, it only means the request was sent to the trading server. It doesn’t guarantee the server accepted and executed the modification. Network issues or server-side validation failures can still occur. For critical modifications, especially in high-frequency strategies, consider implementing a mechanism to check the order’s properties (OrderStopLoss(), OrderTakeProfit()) after a short delay to confirm that the change was applied by the server. If the change isn’t reflected after a reasonable time and potential retries, investigate further using terminal logs or error codes.