Call the default window procedure to provide default processing
#include <WinAPISysWin.au3>
_WinAPI_DefWindowProc ( $hWnd, $iMsg, $wParam, $lParam )
| $hWnd | Handle to the window procedure that received the message |
| $iMsg | Specifies the message |
| $wParam | Specifies additional message information |
| $lParam | Specifies additional message information |
Search DefWindowProc in MSDN Library.