Auto PC controls can trigger events by invoking the ReceiveMsg method on the application’s default IASEventSink interface.
To handle events, applications implement an object that exposes the IASEventSink interface. A pointer to IASEventSink is passed to each form when the form is initialized. A form then passes the pointer to its controls. If a control needs to use the event sink, the pointer should be placed in the EventSink property with IASControl::put_EventSink. It can be retrieved with IASControl::get_EventSink.
To handle events, a control invokes IASEventSink::ReceiveMsg. This method is designed to handle events that use the Win32® format: Msg/wParam/lParam.