Setting a movieclip to the highest available depth

Hi,

I am making a website where I have some thumbnails of images on the first page itself.

These thumbnails are all individual movieclips, acting as buttons…

When a user clicks over a particular thumbnail, the playhead goes to the fourth frame(of that movieclip) and loads a new movieclip (the full version of that thumbnail) already placed at that frame. And as soons he clicks on it again, the playhead comes back to the 1st frame…

Now the problem I am having is that I am not able to place the currently clicked thumbnail’s movieclip to the highest depth…such that when the third thumbnail is clicked and the its bigger version is loaded at 4th frame, the previous two thumbnails are overlaying it due to the depth problem…

I am new to depths, and pls help me out to solve this problem…

Thanks.