Opening a Form Lightbox from a Menu Link

I’m also looking for the answer to this. I have a “Contact Us’ menu item that I would like to open in a lightbox form. I’m following the directions for adding the class “#fl_box-menu-0” in the CSS Classes field, but the link is still trying to go to the “#” that is entered in the URL field. Is there javascript I need to edit to activate this? I appreciate any help!