[AJAX] Updating list for selected category

[liam_d]

Hi all i finally have a working script
http://altercoder.com/ajax/test.php

Select a category and see it change to show whats inside it, only problem is, what if someone finds the one they want, they click it, and it changes any ideas?!

I need a way of a user being able to press something once a category is selected and then update the list, any ideas??

Thanks!!