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.