Ok, Solved it. I was thinking about it in the wrong way (as is often the case with MDX!).
Created a tuple using Ancestor
. This works at the Day, Week and Month levels. I will need to use a SCOPE
statement to control where it is applicable:
MEMBER [Measures].[FY Month Revenue Amount Year Ago] AS
(
Ancestor(ParallelPeriod([Date].[Fiscal].[Fiscal Year], 1, [Date].[Fiscal].CurrentMember),
[Date].[Fiscal].[Month])
,[Measures].[Revenue Amount]
)
It finds the member in the previous fiscal year at the same relative position to the CurrentMember, then gets the ancestor of that member in the Fiscal Month hierarchy.