Dynamic Thumnbail Buttons for my XML gallery

Hi. I downloaded a simple flash XML gallery and I’m currenty trying to modify it to fit my needs. I attached the file.

I am very new to all this, I learned about “attachMovie” and used that to call my button graphic to every thumbnail, its the blue frame that you can see drawn around all the thumbnails.

I wanted it so when I rolled over this button, it would play some effect, or change color or something along those lines but I can’t figure out how to do that… I’ve tried a number of things but can’t seem to get it done by myself. For instance I tried making that movie clip a Button and giving it a different “down” state, but the button doesn’t even work for some reason.

Any help is greatly appreciated, thanks.