Creating a file that has drag and drop feature

Hi,

I'm working on a memory experiment and I want to create a file with a drag and drop feature.  I set an image as layer 1, and several images as layer 2. I would like to create a file where people can drag and drop on of the images from layer two onto a slot in layer one.  Ideally I would like it to remain stable if the place an image in the slot (meaning if they try to place one of the images from layer 2 into layer 1, I want it to allign perfectly).

Help is greatly appreciated.

Thanks.