Do you have a special reason to close a position after 15 seconds?

Please note that if you modify the EA code, it will change the strategy logic and performance. The great value of EA Studio is to help you creating strategies with good backtest stats and corresponding trading results.

Anyway, you can do it easily. Add a global variable in the EA and store there the opening time of your position. At the OnTick function add a check if 15 seconds have passed since the opening and call the ClosePosition function.

Something like that:

long posOpenTime = 0;

void OnTick()
  {
   if(posOpenTime>0 && TimeLocal()>posOpenTime+15)
     {
      ClosePosition();
      posOpenTime=0;
     }

void OpenPosition(int command)
  {
    ...

   if (ticket>0)
     {
      posOpenTime=TimeLocal();
      break;
     }