I'm trying to create a finish variance field on assignments in the Resource Usage view, but I keep getting "#ERROR". Both the Finish and Baseline Finish fields are available on Resources and Assignments, but not Finish Variance. If I try to define the field Finish1 in the Resource Custom Fields with "=[Finish]-[Baseline Finish]", it accepts the formula, but when I insert this column in the table, it doesn't populate. I have also tried checking/unchecking "Roll down unless manually entered" for assignment rows with no success. Any help is appreciated, thanks.
The simple answer is no, you can't, at least not using a formula. Formulas don't get applied to assignments. The "roll down unless manually entered" is exactly that - all the resource assignments for a given resource inherit the custom field value that is computed for the resource using the formula. Though I haven't tried it, I think you could populate a custom resource variance field at the assignment level using vba (i.e. "manually entered"). While straightforward, the effort wouldn't be trivial for anyone who's not accustomed to vba in Project.
Subtracting one date from another date produces a number, not another date. So instead of
Finish1, use a number field, such as
Number1 or a duration field, such as