PROBLEM! Playing a movieclip foward and backwards

I am trying to play a movieclip foward and backwards in the timeline with Action Script 3.0. On my stage will be a movie clip and two buttons (foward and back). When You push the foward button it will make the time line move foward and when you push the back button it will move the timeline backwards. I can only get the time line to move one frame. I dont know how to make the timeline keep moving when the button is held down. Any Help would be great thanks.