[SOLVED] Atahualpa fixed center column!

Hi all,
I have the problem that I need to fix the width of the center column.
It's not working with a fixed layout.

I have a three column project:
The left column has about 20px, the center column 300px, and the right column must be free, because I have my menu right aligned, that it stays always at the very right side of the browser.

I need this, because I have to depict my background photos properly.
I find no way out.

This shows what I mean:
http://www.theaterdegasten.nl/?page_id=5
But with the center column fluid (what I'd like to change)
Thanks for some help.