There are a few ways to do this but one easy way is to make whatever part you want to show through a different color than what you want to stay, place it on the top layer, and than apply the " Chroma Keyer " plug in to remove that color from that layer. Just use the color picker to choose the color you want gone.

Lemme know if this works out for ya.

Good luck;

- Ray

ray@austin.rr.com