what you will want to do is make two main layers, the person and the background. First, make a silhoutte of the person (black) and a white background. Make two copies of your clip and a blank track above each. Apply the silhoutte you made over both tracks and mask them. Do an inverse type mask over the person (because you want to see through the black, not white). Right now it should look like the original clip. Make sure you put the layer of the person on the top. Now apply the ray to the background clip and i think it should work. I don't have my computer so i can't fiddle with this to make sure it's right. If there's a problem you can't figure out just ask.
Hope this solved it,
Elias