Expert Advisor Programming by Andrew R. Young

Advanced Order Placement
Modifying a Pending Order Price
OrderModify() can also be used to modify the order price of a pending order. If the pending order
price has already been hit and the order has been filled, it is no longer a pending order, and the price
cannot be changed.
We'll use the variable NewPendingPrice to represent our changed order price. We'll assume the price
has already been calculated and is valid. Here's how we modify a pending order price:
OrderSelect(Ticket,SELECT_BY_TICKET);
if(NewPendingPrice != OrderOpenPrice())
{
bool TicketMod = OrderModify(Ticket,NewPendingPrice,OrderStopLoss(),
OrderTakeProfit(),0);
}
As always, we retrieve the order information using OrderSelect(). This way we can pass the
unchanged stop loss and take profit prices to the OrderModify() function. Before modifying the
order, we'll check to make sure that our new pending order price is not the same as the current
pending order price.
For OrderModify(), we specify our order ticket, the new order price stored in NewPendingPrice,
and the unchanged stop loss and take profit values represented by OrderStopLoss() and
OrderTakeProfit(). We're not using an expiration time for this order, so we use 0 for the expiration
parameter.
Verifying Stops and Pending Order Prices
Stop loss, take profit and pending order prices must be a minimum distance away from the Bid and
Ask prices. If a stop or pending order price is too close to the current price, an error will result, and
the order will not be placed. This is one of the most common trading errors, and it can easily be
prevented if the trader is careful to set their stops and pending orders a sufficient distance from the
price.
But during periods of rapid price movement, valid stop loss prices can be made invalid by widening
spreads. Different brokers have varying stop levels, so a stop loss that is valid on one broker may be
too close for another. Some trading systems will set stops and pending order prices based on
indicator values, highs or lows, or some other method of calculation where a minimum distance is not
guaranteed.
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