changing z-index of layer with onmouseover on iframe

[natlozt]

Hello!
I have to switch the z-index of two layers dinamically, when the user moves the cursor above an iframe on the page, and restore the originals when the cursor leaves. This iframe is on the first layer, originally below the other.
You can see the problematic page at

http://www.rachegottes.de

if you use any browser other than IE.

Is there any solution for this?