Determines which pop-up window owned by the specified window was most recently active
#include <WinAPISysWin.au3>
_WinAPI_GetLastActivePopup ( $hWnd )
| $hWnd | Handle to the owner window. |
| Success: | Handle of the most recently active pop-up window. |
| Failure: | 0 and sets the @error flag to non-zero. |
Search GetLastActivePopup in MSDN Library.