Playing it all backwards

Okay, so i know how to make the timeline play backwards on rollout in a movie clip, but I am confused as to how to get the whole timeline to play in reverse.

Just say i have two buttons covering my whole stage for the length of my animation. The right button is coded such that on rollover the timeline plays.
I would like to code the left button such that on rollover the timeline plays in reverse.

Please tell me this is actually possible!