Get message of Popup Alert MT4 using - script for MetaTrader 4

this is small script using external DLL "user32.dll".

1. Import Dll and its functions

#define WM_GETTEXTLENGTH 0xE
#define WM_GETTEXT 0xD


#import "user32.dll"
   int FindWindowW(string lpClassName, string lpWindowName);
   int FindWindowExW(int hWnd1, int hWnd2, string lpsz1, string lpsz2);
   int SendMessageA(int hwnd, int wMsg, int wParam, int lParam);
   int SendMessageA(int hwnd, int wMsg, int wParam, char &lParam[]); //Edit lParam to receive value return
#import
//+------

2 Get Handle of Alert Dialog (parent window)

using FindWindowW to specific parent window handle

   int Hwnd = 0; //handle of parent window
   int CHwnd = 0; //handle of textbox
   
   Hwnd = FindWindowW("#32770", "Alert");//replace FindWindowA to FindWindowW for mql4

3. Get Handle of Textbox (or label) in Dialog (child window)

using FindWindowExW to specifit child window handle

   //Get handle of textbox in Dialog
   CHwnd = FindWindowExW(Hwnd, 0, "Edit", NULL);//Find All control have class name is "Edit"

3. Get Content of message from textbox

   3.1 Need to specify the length of the string:

   //Get content of Message in textbox
   //Get length of message string
   int textLength = SendMessageA(CHwnd, WM_GETTEXTLENGTH, 0, 0);

  3.2 Get content

   string contentMsg = "";
   char ch[540];
   for(int i = 0; i < ArraySize(ch); i++) ch[i] = 0x000;
   
   ArrayInitialize(ch, 0x000);
   
   int length = SendMessageA(CHwnd, WM_GETTEXT, textLength + 1, ch);
   
   for(int i = 0; i < length; i++) contentMsg += CharToString(ch[i]);
   
   Print(__FUNCTION__, "--> Content Message = "+ contentMsg);

Get more information for tutorial video: