This attribute is supported for dynamic link library (DLL) access only in Windows. Some DLL routines require that you pass this value.
For ABL window widgets, the Windows window that contains the widget is actually the parent of the Windows widget referenced by HWND. Thus, to obtain the handle of the Windows window that contains the ABL window, you must pass the value of HWND to the GetParent( ) function (in the user32.dll). Pass the result of GetParent( ) to the DLL routine that requires it.