Following is a custom function which when called will return total of active trades for a particular magic number:


Code:
int CountAllTrades(int magic) {
   int c=0;
   for (int j=OrdersTotal()-1;j>=0;j--)
   {
      OrderSelect(j,SELECT_BY_POS,MODE_TRADES);
      if (OrderSymbol()==Symbol() && OrderMagicNumber()==magic) c++;
   }
   
   return(c);
}