Change order of MCs?

OK i am making a storyboard with flash for my uni application.

I am having 12 thumbnails of each of the slides in the storyboard, and I want it so when you rollover each one it enlarges.

I know how to do this, apart from the fact that some of the slides (movieclips) are behind each other. For example, I can make the 12th slide enlarge onRollover, but it is behind all of the previous slides…

Is there a way to dynamically change the order of movieclips?

I hope this makes sense, i found it hard to describe the problem well…