GetTopWindow    
The GetTopWindow
function examines the Z order of the child windows associated with the
specified parent window and retrieves the handle of the child window at the top
of the Z order. 
HWND GetTopWindow(
| 
       HWND hWnd   | 
  
   // handle of parent
  window  | 
 
| 
      );  | 
  
   | 
 
Parameters
hWnd
Identifies
the parent window whose child windows are to be examined. If this parameter is
NULL, the function returns a handle of the window at the top of the Z order. 
Return Values
If the
function succeeds, the return value is the handle of the child window at the
top of the Z order. If the specified window has no child windows, the return
value is NULL. To get extended error information, use the GetLastError function. 
See Also