Photoshop :: PS-CS4 How Do I Make Type That Reverses

I have a black silhouette, and I want to lay a large headline over it so that the type is black when it's over the white background and changes to white as it moves over the black silhouette. The edges of the silhouette cut through the middle of a couple of the letters, so I can't do this letter-by-letter. I think there must be a simple way to do this that begins with rasterizing the text (which is the same as "create outlines" in Illustrator, right?)