How can I block out dates on a form once they have been selected by a registrant?

I am looking to use JotForm to schedule individual appointments with various parties.  Once a party schedules an appointment with me for a certain time slot, I want that time slot to disappear for any future registrants.  How can I accomplish this through JotForm?

Simply add this widget to your form, this has the feature you're looking for http://widgets.jotform.com/widget/date_reservation.

So once the user picks a date and submits the form, the selected date can no longer be selected again.

Regards!