MQL5 - how to modify limit order

[vovanchau27]

my code just modify open order,
It can not modify limit order.
how to modify limit order?

for(int i = (int)PositionsTotal(); i >= 0; i--)
     {
      ulong positionTicket = PositionGetTicket(i);
      if(positionTicket == 0)
         continue;

      if(PositionSelectByTicket(positionTicket))
        {
         if((PositionGetInteger(POSITION_TYPE) == OP_BUY ||PositionGetInteger(POSITION_TYPE) == OP_BUYLIMIT) && PositionGetString(POSITION_SYMBOL) == Symbol())
           {
            trade.PositionModify(positionTicket,PositionGetDouble(POSITION_SL),selectedPrice);
           }
        }

     }

[Yashar Seyyedin]

You may check the documentation.