Theme Editing Help Wanted – Adjust Column Width

Hi,

I would like to adjust the two columns on the right in the following theme to be able to fit a 320×250 banner ad in the top right:

http://www.solostream.com/2007/06/08/worpdress-blog-theme-zeke-10-widgets/

my blog is at http://www.nybodyboarding.com

Is it possible to make the far right column a little wider to fit the 300z350 ad, and shrink the middle (smallest) column?

Thanks