I've never actually used the Calculation part of field validation, but here's what I'm wanting to do.

I have a tasks table, inside that table I have a Date Field, a Start Time Field, and an End Time Field.

No records start time and end time can overlap another records. And I need a way to check for that. Sure, I could use a script to do this, searching by date and then checking the times recrod by record.

But then I got to thinking about List and GetNthRecord functions and wondered if this might be possible in a calculation. Just wondering what a few of the more experienced users think here.

I think I would define a self-join relationship between overlapping records, excluding the current record (by adding SerialID ≠ Overlap::SerialID). Then you can validate by

not Overlap::SerialID

I think I would define a self-join relationship

Wouldn't it be self-joins in plural, since stacking with OR havn't found it's way into relations def... ?

--sd

timespans.zip

Wouldn't it be self-joins in plural

I don't think so.

ValidateOverlap.fp7.zip

Ah! Yes - DeMorgan....

--sd

Brilliant comment. I still don't quite understand how the "not Overlap::SerialID" is how it validates though. Mind dumbing it down a bit for me :/

"not Overlap::SerialID" means there's no related record in the Overlap TO. Unless you do have a record that overlaps, but it doesn't have a SerialID, or has a zero as its SerialID value.