jQuery UI Multiselect - How to adjust column widths?

jQuery UI Multiselect - How to adjust column widths?

Hello all!

I have a quick question about the jQuery UI Multiselect.  

I have searched through the CSS files and have not been able to figure out how to adjust the width of the two columns (selected & available). I can adjust the width of the entire control, no problem, but how do I change the proportion the two columns take?  At the moment it's always about 2/3rds of the width for the Selected column, leaving only 1/3rd for the Available column.   My desire is to have them both take 50% of the total width.

Any ideas?

Many thanks in advance!
Mike