Expert Advisor Programming by Andrew R. Young

Order Management
The while Operator
The while operator is a simpler method of looping in MQL. The for loop is best if you know exactly
how many times you plan on executing the loop. If you're unsure of the number of iterations
however, then the while loop would be more appropriate.
Here's an example of a while loop:
while(Something == true)
{
// Loop code
}
This literal example uses a boolean variable called Something. If Something is equal to true, the
loop will execute. Of course, if the value of Something never changes, the loop will run endlessly.
Thus, it is necessary that there be a condition to change the value of Something at some point
during the loop. Once this condition is true, Something is changed to false, and the loop will stop
executing.
You could also increment a variable, just like you would using the for operator:
int Counter = 1;
while(Counter