MT4: 

//--- importing required dll files  #include <WinUser32.mqh>  #import "user32.dll"  int GetAncestor(int, int);  #define MT4_WMCMD_EXPERTS  33020  #import    //+------------------------------------------------------------------+  //|                                                                  |  //+------------------------------------------------------------------+  void SetAlgoTradingTo(bool trueFalse) {      //--- getting the current status      bool currentStatus = IsTradeAllowed();      //--- if the current status is equal to input trueFalse then, no need to toggle auto-trading      if(currentStatus != trueFalse) {          //--- Toggle Auto-Trading          int main = GetAncestor(WindowHandle(Symbol(), Period()), 2/*GA_ROOT*/);          PostMessageA(main, WM_COMMAND,  MT4_WMCMD_EXPERTS, 0 );//Toggle Expert Advisor button      }  }

MT5: 

//--- importing required dll files  #define MT_WMCMD_EXPERTS   32851  #define WM_COMMAND 0x0111  #define GA_ROOT    2  #include <WinAPI\winapi.mqh>    //+------------------------------------------------------------------+  //| Toggle auto-trading button                                       |  //+------------------------------------------------------------------+  void AlgoTradingStatus(bool newStatus_True_Or_False) {      //--- getting the current status      bool currentStatus = (bool) TerminalInfoInteger(TERMINAL_TRADE_ALLOWED);      //--- if the current status is equal to input trueFalse then, no need to toggle auto-trading      if(trueFalse != newStatus_True_Or_False) {          //--- Toggle Auto-Trading          HANDLE hChart = (HANDLE) ChartGetInteger(ChartID(), CHART_WINDOW_HANDLE);          PostMessageW(GetAncestor(hChart, GA_ROOT), WM_COMMAND, MT_WMCMD_EXPERTS, 0);      }  }  //+------------------------------------------------------------------+