pie chart wheel animation

Hi there! I have created something very similar to this using the pie shape that wheels on for the entrance animation, but I'd like to take a step further and can't figure out a way. Imagine if that same graphic wheeled on, gave you the 82% stat, and then the pie shape does a sort of reverse wheel so that only 18% of the shape is showing and then the stat changes to "18% of facts are true". I can't figure out how to do this backward animation. I have some audio that throws out a lot of stats one after another, so I was hoping to have the wheel adjust to match the percentage being spoken. Any ideas how to accomplish that? I can think of ways to have the pie fade in and out to different shapes, but I really like that wheel motion here.