A select-function for WWF Inbox

I´ll hope someone can help me! I didn´t now if I should post this mess here or in the WWF-section...

This is what I want:
In the pm_inbox.asp you can select/un-select all the PM messages. And this is done with javascript. Now I want to do a function to select just the read messages. So when you´re clicking on a link it selects all the read messages and then you can delete them. How can I do that?