Conditional validation

[alexliz]

I have a system for registering sales and Sales People. Each Sales Person belongs to a Branch, and some Branches have Departments. I want to make sure that the Dept is entered for those who belong to Branches WITH Depts. On the other hand, I don't want the validation to be triggered when there are NO Depts for the particular Branch the Sales Person belongs to. Branches are kept in one file, Depts in another. I 've tried Validate by Calculation:

Case(Count(bsg|fk_branch_id::pk_dept_id)>0, not(IsEmpty(fk_dept_id)), "")

but it doesn't work. It keeps demanding that a value be entered in fk_dept_id even for those Sales People who belong to a Branch with no Depts registered for them.

Any ideas?