Sort thumbs based on XML attributes

Sort thumbnails by xml attributes
Hello, I have a photo gallery with rows (and columns) of thumbnails generated by xml and a Flash For Loop.

What I want is to have a drop down box with options that will say “New York”, “Philadelphia”, “New Orleans”. When a user chooses one it will trigger a function that would ‘look’ into my XML file for a “Philadlephia” or “New York” XML Attributes and then only loop those photographics tagged with that particular Attribute.

I have been trying to figure this out for a while and I am not getting anywhere…

Can someone help me out a little on this?