I’m not sure if there is a solution to this… especially since not all users may see the exact font size that you set, making the middle column longer or shorter. If they choose to change the text size to make it easier for them to see (heck, I’m only 22, and I had difficulty looking at the 11px text) that column will adjust to fit.
As a side note, your site isn’t WCAG compliant, despite the image on your site saying so, since users can’t resize the text on IE (because the text is in px, rather than in ems).
