Powerpoint timer help !

[aiman]

Hello, I am trying to make a game. But I am stuck figuring out just this one function. A timer that initiates at slide number 3(it will not affect the presentation,(clicking, hyperlink, going to the next slide, macro, transitions, etc, like an invisible background-running macro), and when it goes off(after 2 minutes maybe?), no matter at whatever slide number, or whatever it is that the user is doing during the active presentation, it would go to slide number 20(for example)...
Help me please... Thanks....