Powerpoint auto-return from custom slide show to default loop in touch-screen kiosk mode

I am developing a touch-screen kiosk application in PowerPoint (using 2010 version on a PC) that consists of a loop of slides automatically progressing every 5 seconds. Each slide has a common navigation button that allows the user to go to a menu slide from which they can navigate to a range of custom slide shows within which they can navigate forward and reverse or return to the menu slide or default loop. My problem is how to make the show return to the default loop after a minute or so if the viewer walks away in the middle of a custom show.