Forms inactivity warning?

There is an event MAX_INACTIVITY_EXCEEDED in TimeoutPJC.class in timeout.jar, which is part of Forms demos pack.  This event can be used in a form to trigger an action if the inactivity timeout setting is exceeded.  Has anyone implemented a MAX_INACTIVITY_WARNING event, which will trigger at a set time (like timeout - 5) to warn the user their session is about to time out?