Hi Mack,

Your a diamond among the gems....fixed it...using your reply...gone back and determined the first child and created the set...and then did a tail on it....

-- Previous 3 month sales using tail

WITH MEMBER [Measures].[PrevThreeMonthSales] AS 'SUM(Tail([Order Date].[CalendarHierarchy].CurrentMember.Parent.Children(0):[Order Date].[CalendarHierarchy].CurrentMember,3), [Measures].[Sales Amount])'

SELECT {[Measures].[Sales Amount], PrevThreeMonthSales} ON 0,

[Order Date].[CalendarHierarchy].[Month] On 1

FROM MyFirstCube