Multiple Entry SELECT and JavaScript interaction

I have a curious problem that I don't have a clue how to solve that's probably simple but I can't find it documented anywhere. It might be the first PHP-induced limitation I've run into... In order to allow multiple entry on a <SELECT> form object, the name of the form has to end with the brackets [], but then when I do that I can't refer to it from within JavaScript because as a variable name it becomes illegal. I have to be able to refer to the SELECT object to change its contents based on another form object. I've tried all kinds of things to work around this, but I'm stuck. Any ideas out there? Thanks, Sean