There is a field called venue on the opp. There is the same field on the user card. If the booking is confirmed (a field on the opp) this should show the full form to the users who's venue field is the same as on the opp... otherwise all other users should only see some of the form (and shouldn't be able to search the fields they cannot see) on
and if the booking is not confirmed who can we hide this field from advance find