Modify Javascript Errorcheck w Profile Update

Hi,

I have created a custom registration field that only displays after the user has initially registered using the [s2member -profile /] shortcode.

I would like to add some Javascript error checking to the one custom field (multi-checkbox) to make sure that if a certain checkbox is checked, then no other checkboxes are checked, throwing a Javascript error to the user if this is the case. How can I add this to my code?

Thanks,
Tim