Not allowing double booking

[8mycsh]

I have an appointment calendar that I am creating for a client. I have thought about evrything but one thing and I am not sure of the best way to go around it. When they enter an appointment for that day at a certain time I don't want them to be able to book again. I would like to do a javascript box "appointment already exists! (or something like that)

I have done a search here on the forum and I am curious can I control this at mysql or through php.

If so how would I go about doing it.

Thanks for your help.

[drawmack]

I would create a table called filled times. Then every time they make an appointment break it down into 15 minute entries in this table. Then just check the each fifteen minute interval against this table.