Extensible document business rule

This sounds like the sort of thing that is better suited to a Dynamic Calc formula, strategically placed on a UD8 member, reacting to an Annotation-type View member. You then just reference the intersection in a regular Extensible Document field.

Very rough example:

If api.View.IsAnnotationType() Then
    Dim diff as Decimal = api.Data.GetDataCell("T#2024 - T#2023").CellAmount
    If diff > 0 then
      return "Profit"
    else
      return "Loss"
    End If
End If
Return Nothing

Extensible Documents are not meant for calculations; they are meant to embed data that has already been calculated by the engine.