Hi, i created a customer form, with a reservation subform on it. This acts as my customer reservation form for inputting new customers and reservations, or adding a reservation to a current customer. IS there any way in which, once the property has been selected from a drop down menu, i can make it so that a specific date for that property can only be chosen once, so as reservations can not over lap/ run into each other, as double booking is a serious issue. There is already a property form, but it only displays info on the propery's physical attributes. thanks.

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Richard Replies:

You could query your reservations table to see if there was already something booked for that date/time, but I warn you that this is going to involve a little programming.

For example, let's say that you have a date/time field called AppointmentTime. You want to see if there are any appointments in your table that fall on that exact date and time. In the AfterUpdate event for that field, you could say:

ID = DLOOKUP("AppointmentID","AppointmentT","StartTime=#" & AppointmentTime & "#")
If Not IsNull(ID) Then
   MsgBox "You've got another appointment scheduled at this time"
End If

This uses the DLOOKUP function to look in the table AppointmentT and see if there is a record with a StartTime equal to your AppointmentTime value. If so, it brings back it's AppointmentID. If not, you get a NULL.

Now, what you want to do is a little more complex, so you'd have to probably use DMAX and DMIN to see if appointments overlap each other, but it's not terribly different.

Here's a tutorial that will help you more with DLOOKUP if you would like to pursue this further:

http://599cd.com/tips/access/dlookup-function/?key=AlExBlg

It's one of the most powerful functions in Access. Once you master it, you really add a TON of flexibility to your databases/.

Hope this helps.