All Open32 controls, unlike Windows controls, notify their parent when focus changes. Care needs to be taken when processing WM_COMMAND messages from controls so that proper handling based on control type is accomplished. You may receive a WM_COMMAND notification from Open32 that you do not receive from Windows causing unpredictable results. A well-structured program should not encounter problems related to these extra notifications. Open32 applications can also be enhanced to take advantage of these additional notifications to provide OS/2-only additional functionality.