Two tables:

Tutor - holds records of tutors

Associate - holds records of associates (students)

One tutor to many associates.

I have a form on each one. I have a report on associates which is grouped on tutor so shows each tutor with their associates. I have a report on tutors. I'd like it to include the count of associates against the tutor. The Associate form has a field which is a lookup to the Tutor "name" field.

I've tried adding a formula field to the tutor form, with an expression based on the Count function - something like count(Associate[tutor.name=input.ID]) (I've tried lots of permutations of this). All I get is an error saying "Expression not supported in forumla". Is this not supported? All the examples for formulas just refer to fields on the current form. Are joins not possible? In SQL this would be (select count 1 from associate where associate.tutor=tutor.id)