Table Column Widths

Hi, I'm using the Catch Box theme and it is the first theme I've had this problem with. Every time I try to create a 3 column table, the third column is about 10% of the total table width, making it squished up against the right side of the page. I've tried every html code I can think of and Google could suggest, but none would override what I am assuming is the CSS template dictating the column widths. I do not have pro to edit the CSS. Is there any way to modify the widths of the columns so that the third column is balanced with the others? (and yes, I'm using a table for data, not for formatting the layout of the page) Thank You, Lacey