Flash Animation Assistance Needed

I have a project I'm working on and I am really stumped on making a seemingly simple animation work.

The animation is of a coin scratching off a layer to reveal the layer beneath. I have the开发者_StackOverflow社区 coin animated, and the layers in place. I am wanting to know if there is a way to erase/delete every place the coin passes over the stage, revealing the layer beneath. I've seen animations where ActionScript is used to allow a user to control the coin/pointer and activate the "scratch-off" effect. However, I am trying to come up with a method that is not a user-initiated animation since I want the effect to repeat in several places in the timeline.

For the life of me I cannot figure out how to make this work. I am a moderately skilled Flash user and an ActionScript novice.

I am using Flash CS4 on a SnowLeopard Mac.

Any assistance or advice would be appreciated. Thanks.

You need to put the layer you want to reveal on top of the layer you want to show to begin with. Then you use a mask to reveal the parts you want to. You can animate the mask layer like any other layer, either using a tween or a frame-by-frame animation.