Layers and Checkerboarding

Hi,

I'm a little stumped with my new project and was wondering if someone could help me please? I'm taking classic movie images, making them into black and white silhouettes and trying to make a montage style thing of some great film noir images. Its all going well, got the making of the silhouette down but now comes my quandary.

Each image will overlap another slightly and where they overlap i want the top one to switch to an inverse of itself. For instance if the bottom layer is black when part of the layer above is overlaid only the section which overlaps becomes white in a kind of checkerboard effect.

I'm really new to Photoshop so if someone could help me or point me in the right direction I'd really appreciate it.

Thanks

Ollie

alter the layer blending mode of the top layer ~ i think "overlay" will do it??