jQuery Validate plugin conditional required field

I'm having an issue with the jQuery validate plugin. I have a set of 3 radio buttons, if either of the first two are selected, the user is shown an extra select input on the form, if the third is selected, nothing happens. I want to user to be required to select something from the additional select input if they choose either option 1 or 2 from the radio button set. I've written the code for the f