RoundedCornersExtender & Panel control

How do I assing a controlID to more then one panel control.

I would like to use one RoundedCornersExtender with about 3 panel controls.

Is this possible?

You should create 3 instanes of RoundedCornersExtender - one for each of the 3 panels.

This should be done in the code behind?

Im using C#. Could you just show me how to do one plz.

After I create an instance I should assing that panel as the target control of the roundedCornerControl ?

There's an example here:http://ajax.asp.net/ajaxtoolkit/RoundedCorners/RoundedCorners.aspx
This example demonstrates a problem I am having with rounded corners. When the corners are configured, the height of the panel changes dynamically. This is really annoying to see during page load in the browser, as the content of the page slides down right after the page is finished loading. How can I work around this? (i.e., I tried setting margin styles in the panel and this does not work).

This example show it using one panel & a RoundedCornersExtender.

I would like to use 5 panels & one RoundedCornersExtender. Any suggestions ?