Custom Appointment Form

Please submit your best bid. No automated bids will be accepted. I need either an appointment/reservation form modified to accept paypal payments/deposits. Deposit will be calculated by the form script so as to prepopulate value for paypal. Integration of PayPal via IPN/API is required, so if you do not have experience with PayPal do not bid. The overall functionality of the form must be this: front-end: 1. user must input all required fields. 2. paypal deposit must be calculated for the user and populated into payment page via IPN/API. 3. user can select dates available from a calendar with unavailable dates blacked out unable to be clicked on. 4. upon selecting a date and time, and making paypal payment, the time selected becomes unavailable on calendar. back-end(admin): 1. must be able to preselect times and days available. 2. must be able to check reservations. There are many reservation scripts out there now, I don't mind a modified one or one from scratch as long as it works. The script should also be templatable. I don't care what language is used as long as security is ensured and no SPAM gets through your script. I'm willing to pay up to the budget maximum, 25% down and 75% upon completion. Good luck!