#include <WindowsConstants.au3>
#include <GUIConstantsEx.au3>

$Gui = GUICreate("WM_NCLBUTTONDOWN", 500, 150, -1, -1, $WS_OVERLAPPEDWINDOW)
GUISetState()

GUIRegisterMsg(0x00A1, "WM_NCLBUTTONDOWN")
while 1
Switch GUIGetMsg()
Case $GUI_EVENT_CLOSE
    Exitloop
Endswitch

wend

Func WM_NCLBUTTONDOWN($hWnd, $MsgId, $wParam, $lParam)
msgbox(0,"Сообщение","нажат заголовок окна вроде бы!)))")
EndFunc