Buttons Cut Through Each Other!

[Sputniks]

Here is a link to a very simple flash file:

http://pashart.net/buttonTest.fla

The problem is....Thre are six buttons in this Flash document. When the mouse rolls over of one of the buttons it gets larger in size...so large that it is supposed to get above the other buttons and hide them underneath. But the buttons underneath of enlarged button simply cut through it....like masking it away.
What should I do in order to stop this from happening?
Thanks in advance!

[oldnewbie]

You'll have to convert them to button movie clips and swap depths on them, so that the current rolled over button mc is always at the highest depth.

[Sputniks]

How do I swap the depths of the button when a mouse rolls over it?
Is there ActionScript command for it?
Please forgive my incompetence, but why the button should be a "movie clip button"....and how is it being done? Is it because that command that changes a depth works only with Movie Clips symbols? What is the name of the command?
Thanks in advance~