Variable Loading and If Formula

Hey People,

How would I go about making:

If (flash.swf?name=something) equals “something”
Then change the brightness of a button object to 0, I.E. it’s -62 when it’s not being hovered over.
Oh, and I would like to know how to do the equivalent of a PHP “isset” function for the variable as well, so I could change the url of a link.