Play, perhaps slower or faster

Hi all,

well, I`ve been devloping a flash template for presentation (b/c PPT is just a little too lame sometimes). This is how it works: Each frame represents a slide…naturally. With mousclick or arrows you can navigate.
Beyond that, I would like to integrate a auto play function.

I would like to use the + and - keys to do so. So if on screen 7 I suddenly decide I can talk according to the auto speed - I hit the + button. if the auto speed is to slow hit it again and it`ll go faster. Same with reverse (not that makes much sense, but maybe opens a few more ideas of how to present).
And if I want to return to manual navigation, lets say…hit the *.

I think this should work with setinterval - but I`m not sure with the speed, adjust speed and ahhhh - not sure about the whole thing.

Thanks for your help,