Calc based on multiple records in related file
I've been out of Filemaker for a while but am having to step back into it so I'm a little rusty to say the least!
Anyway, I have 2 tables
The vehicles table simpley holds records of individual vehicles.
The mileage table holds the mileage reading and the date that it was taken and of course a relationship back to a vehicle.
I need to work out the average mileage per annum of a vehicle based upon the miles travelled between the dates in the Mileage table. the sum is easy enough, I just can't seem to translate this into filemaker and get the calc to work across the different tables.
Any help is appreciated, let me know if you need any more information.
P.S I would probably end up limiting the calc to the last two mileage readings as they will be the most up to date.