Make _xscale larger when onRollOver, but need to swap depths

I am making a photo gallery with thumbnails and when the mouse rolls over them, they increase in size. Problem: when they increase, they do not cover the other thumbnails completely, since it is only an _xscale percentage increase and not a new movie clip. So you can see all the other thumbnails over the increased photo size.
It is a problem of swapping depths I’m sure–but do I have to take off all the thumbnails from the main level and load them dynamically onto different levels in order to be able to swap depths?

Thank you:hr: