Modify existing script of a menubar

We have a menu bar on the top of each page which is a SSI and therefore exactly the same on every page of a website. What we need is for someone to alter/adjust the script so that each menu heading can be adjusted for width. As it is now the heading adjusts to the width of the text contained in the heading. Ideally there would be a parameter within the script where we would only have to enter a value for the heading widths once and then all headings would be equal to the value we entered.