[jQuery] How do I compare two form fields using the form validation plugin?

[Matt Wilson]

I have a form with two radio button lists.  Each list has the same set
of choices.  I want to make sure that something is checked in both
lists and that the value in the first list is not the value in the
second list.

I know I could write my own submit handler to do this, but I'd like to
work within the jquery form validation plugin because I already use it
in other places.

Any ideas how to do this?