Form for booking an appointment using dataselect

Dear Perchers,

I need to make a form for booking appointments where a customer fills in his/her name, email and selects a date from a list. The date could come from a dataselect, enabling the provider to continuously add new dates.

The task I am not able to solve is that the given date should be removed from the list when the form is submitted.

Could you recommend a solution to this?

Thanks a lot in advance!
Laszlo