How can I add List Selection into php description?

I have a load of multi record lists.

There is a drop down list with the following in each list:

mil | Military
med | Medical
saf | Safety
aer | Aerospace

Basically I have a sidebar with a load of multi list titles and url's used for sub navigation. When a new section is added to the multi record it displays the title in the sidebar nav. All works nicely.

When you go to the actual multi record detail page, I would like the sub nav to indicate it's active using css. I have seen this article and like the idea of using php to indicate the correct title and change it's colour. http://www.alistapart.com/articles/keepingcurrent/#

Now, as you can see above I have 3 letter description for each section, like mil, med, saf etc.

<?php $thisPage="About Us"; ?>

How can I replace the above "About Us" to display the chosen drop down list. For example: <?php $thisPage="mil"; ?>

Once I have this I can then crack on and add the css etc.

Any ideas? Thanks Jono