I've written a query that checks to see if a double booking has been made 
in my room bookings database.  Please help me to actually put this into 
my form before_update module (or macro).  I have the fundamentals of what 
I need, but cant use it. I have no idea how to do this.  Any help is 
gratefully received. Here is my calculated query field....

NoClash: Nz(([tblBooking_1].[Time Start]>=[tblBooking].[Time Finish]) Or 
([tblBooking_1].[Time Finish]<=[tblBooking].[Time Start]) Or 
([tblBooking_1].[Date]<>[tblBooking].[Date]) Or ([tblBooking].[Room]<>
[tblBooking_1].[Room]) Or ([tblBooking].[UniqueID]=[tblBooking_1].
[UniqueID]),False) - and the criteria is set to false.