[traderdoc]

double LastOpenPrice;
for(int i = OrdersTotal() - 1; i >= 0; i--) {
   if (OrderSelect(i, SELECT_BY_POS, MODE_TRADES)) {
      if (OrderSymbol() == Symbol() && MagicNumber == OrderMagicNumber() ) {
            if (i == OrdersTotal() - 1) LastOpenPrice= OrderOpenPrice();
...
      }
   }
}
//oder gleich
double LastOpenPrice;
if (OrderSelect(OrdersTotal() - 1, SELECT_BY_POS, MODE_TRADES)) {
   if (OrderSymbol() == Symbol() && MagicNumber == OrderMagicNumber() ) {
      LastOpenPrice= OrderOpenPrice();
...
   }
}

traderdoc