setting the size of a layer and animating a grid of images

Hi all,
I am trying to animate a grid of nine different frames. I’ve attached an image to roughly show what I am trying to do. I can’t seem to get my head around what seems like a very easy idea. I want each layer to be 1/9th of the frame with distinct edges. Other programs have a picture-in-picture function. I’m thinking I’d set up 9 separate layers and then use the cutter maybe? Ack! Any suggestions would be welcome.