how to add line down right side of main content area?

I've finally gotten my site to look how I want, minus one part that I cannot seem to figure out. I want to have a border line along the right side of the main content box. I fyou look at the site: http://littleturtleknits.com/zencart/ I want the line to run from the bottom right corner of the brown area to the top right corner of the yellow footer area. Is there a way to do this? I've fiddled around with various border options I found searching here, but all of them put borders around the whole area, or the entire page.

These will both do what you want in your case:

#contentMainWrapper {border-right: 1px solid #112233;}
#centerBackground {border-right: 1px solid #112233;}

This would normally do it, but your added #centerBackground div and the padding or margin at the bottom make it not quite reach:

.centerColumn {border-right: 1px solid #112233;}

Fantastic! Thank you so much!

Looks like it worked a little too well! ;)
I didn't mean for you to add borders to both .centerColumn and #centerBackground; one of them is enough, and .centerColumn doesn't reach all the way to the bottom.