.NET Development using SMS

This task is to write a service so that someone can enter an appointment and then they receive an SMS message to their phone to remind them. Hence the functionality is as follows: 1. User enters their number, and their name 2. User enters a date (calendar) and time for their appointment. User enters the reason for the appointment, eg doctor, dentist, taxi, other. 3. User enters the reminder period, eg 20 minutes before the appointment 4. Systems send an SMS message before the appointment. System: SQL SERVER, VS 2010, .NET 3.5, C#. No clever web site design is needed. All numbers are UK ones.