I'm wanting to add a date range to a booking record which features a start date and end date. When submitted it will check another table for already taken dates and return a result as whether it is avaliable or not.

I've done this before with PHP/Mysql but I'm having a mental block on how to do it in Filemaker 7.

Can anyone give me a kick start?

Try this multi-criteria range relationship (double click the relationship line on the table occurence graph to get at the Edit Relationship dialog)

Interface <=> Booking =

Interface::Room = Booking::Room

AND Interface::StartDate <= Booking::EndDate

AND Interface::EndDate >= Booking::StartDate

You can add additional criteria to filter by additional things, like Sites or something.