#property copyright "system 1"
#property link	  ""
#define   MAGIC	01901

.
.
.

if ( ExistPosition() == False) {
OrderSend(Symbol(),op,Lots,pp,SLIPPAGE,ldStop,ldTake,lsComm,MAGIC,0,clOpen);   // MAGIC  =  system 1

}


// if  open 1 position only for system 1 MAGIC ?
bool ExistPosition() {
  bool Exist=False;
  for (int i=0; i<OrdersTotal(); i++) {
	if (OrderSelect(i, SELECT_BY_POS, MODE_TRADES)) {
	  if (OrderSymbol()==Symbol() && OrderMagicNumber()==MAGIC)  Exist=True;
	}
  }
  return(Exist);
}