[Plugin: Modal Dialog] Required Fields

I’ve installed the modal dialog pop up, but it does not force users to enter either select a mailing list or to enter information into the required fields. If either of these are not done, when the user presses the subscribe button, the pop up closes, and they are redirected to the page that they were on. But none of the information that they did enter is captured. Any suggestions?

http://wordpress.org/extend/plugins/modal-dialog/