Timetable Validation Through Form

Hi All,

I have a problem regarding how to validate data that the users of my database must enter. I have two tables that relate to this. The first it a booking table.

This table named tblBooking contains:

Booking ID
Client
Date
Label (Name of the Timetable slot)
Event Name
Paid?


The second table contains all the information on the timetable slots. These slots are 10:30am to 12pm(Morning), 1pm to 5pm(Afternoon), 6pm to 9pm(Night), and 6pm to 11pm(Late Night).
The table is called tbltimetable and contains:

Label
Start Time
End Time
Cost


The problem is that a user can enter the database, open the booking form, and enter conflicting data. E.G two clients can have the same 6pm to 9pm booking, on the same date.

Another problem is that the final two slots of the time table are also conflicting, e.g, one client can have a 6pm to 9pm booking, and another can have a 6pm to 11pm booking.

Obviously, neither of these situations are possible, so I wish to add some validation that will prompt the user to choose another date when they pick a date/timetable slot combination that has already been taken.

I assume that I will have to impliment this using the forms, as it is not possible to add this amount of validaition in the table design. The thing is, I dont have any ideas on how to do this, and I have only just started to learn VB if that is what i have to do. If anyone can give me any feedback and help me to learn how to solve this problem, either through the booking form, or a better way, then I would be very grateful.

On another note, i would have posted the database, but it is 41mb, and only has about 10 records in each table. Does anyone know why this could be? I have already compacted and repaired the database, as it used to be 39mb.

If you have any questions please do not hesitate to contact me.

Thanks for taking the time to read my post.
Best Regards
Chris Grant