Calculation to sum a sub-set of records in related table
I am a Filemaker Newbie. I have 2 tables: Donors and Donations. They are related by a join on Name and Address fields. And it is a 1:many relationship from Donors:Donations.
Now I need to display on the donation entry form a field that summarizes the amount for a specific SchoolYear:
CurrentYearTotal = sum(Donations Amount) where SchoolYear = "2012-2013".
How do I define this calculation field? I was able to define a calculation field on the Donors table = Sum(Donations::Amount). But how do I add the filter/where condition to only sum over records only for the current year. Thanks.