The author of the idea: ef91 (the beginning of the related discussion #62)

MQL5 code author: Vladimir Karputov.

The EA waits for a TP or SL to trigger, and then opens a position in the opposite direction. It checks if there is enough money before sending a trade request. OnTradeTransaction.

For example, we have an open Buy position. Once TP or SL triggers, a new Sell position is opened. Then, after triggering of TP or SL, a new Buy position is opened.

A deal closure is monitored in "OnTradeTransaction":

//+------------------------------------------------------------------+
//| TradeTransaction function                                        |
//+------------------------------------------------------------------+
void OnTradeTransaction(const MqlTradeTransaction &trans,
                        const MqlTradeRequest &request,
                        const MqlTradeResult &result)
  {
//--- get transaction type as enumeration value 
   ENUM_TRADE_TRANSACTION_TYPE type=trans.type;
//--- if transaction is result of addition of the transaction in history
   if(type==TRADE_TRANSACTION_DEAL_ADD)
     {
      long     deal_entry        =0;
      long     deal_type         =0;
      string   deal_symbol       ="";
      long     deal_magic        =0;
      long     deal_time         =0;
      if(HistoryDealSelect(trans.deal))
        {
         deal_entry=HistoryDealGetInteger(trans.deal,DEAL_ENTRY);
         deal_type=HistoryDealGetInteger(trans.deal,DEAL_TYPE);
         deal_symbol=HistoryDealGetString(trans.deal,DEAL_SYMBOL);
         deal_magic=HistoryDealGetInteger(trans.deal,DEAL_MAGIC);
         deal_time=HistoryDealGetInteger(trans.deal,DEAL_TIME);
        }
      else
         return;
      if(deal_symbol==m_symbol.Name() && deal_magic==m_magic)
        {
         if(deal_entry==DEAL_ENTRY_OUT)
           {
            if(deal_type==DEAL_TYPE_BUY || deal_type==DEAL_TYPE_SELL)
              {
               if(deal_type==DEAL_TYPE_BUY)
                  m_close_pos_type=POSITION_TYPE_SELL;
               else if(deal_type==DEAL_TYPE_SELL)
                  m_close_pos_type=POSITION_TYPE_BUY;
               else
                  return;
               m_is_trade=true;
              }
           }
         else if(deal_entry==DEAL_ENTRY_IN)
           {
            m_is_trade=false;
           }
        }
     }
  }

Check volume before OrderSend (consider the opening of a Buy position as an example):

//+------------------------------------------------------------------+
//| Open Buy position                                                |
//+------------------------------------------------------------------+
void OpenBuy(double sl,double tp)
  {
   sl=m_symbol.NormalizePrice(sl);
   tp=m_symbol.NormalizePrice(tp);

//--- check volume before OrderSend to avoid "not enough money" error (CTrade)
   double check_volume_lot=m_trade.CheckVolume(m_symbol.Name(),InpLots,m_symbol.Ask(),ORDER_TYPE_BUY);

   if(check_volume_lot!=0.0)
     {
      if(check_volume_lot>=InpLots)
        {
         if(m_trade.Buy(InpLots,NULL,m_symbol.Ask(),sl,tp))
           {
            if(m_trade.ResultDeal()==0)
              {
               Print("Buy -> false. Result Retcode: ",m_trade.ResultRetcode(),
                     ", description of result: ",m_trade.ResultRetcodeDescription());
              }
            else
              {
               Print("Buy -> true. Result Retcode: ",m_trade.ResultRetcode(),
                     ", description of result: ",m_trade.ResultRetcodeDescription());
              }
           }
         else
           {
            Print("Buy -> false. Result Retcode: ",m_trade.ResultRetcode(),
                  ", description of result: ",m_trade.ResultRetcodeDescription());
           }
        }
      else
        {
         m_is_trade=false;
        }
     }
   else
     {
      m_is_trade=false;
     }
//---
  }