If I understand the requirement, I believe this will help. You can run it against the Warehouse sample cube with the MDX sample application (Note that spacing in the syntax might be off, due to my pasting it into the area below):

WITH
MEMBER
[PRODUCT].[Alko-Dairy]

AS
'AGGREGATE({[Product].[All Products].[Drink].[Alcoholic Beverages], [Product].[All Products].[Drink].[Dairy]})'

SELECT

{[Measures].[Units Shipped], [Measures].[Units Ordered]} ON COLUMNS,

NON EMPTY { [Store].[Store Name].Members }ON ROWS

FROM

[Warehouse]

WHERE

([Product].[Alko-Dairy])


Let us know if this doesn't answer the need, and why, and I'll get back as time is available. Thanks for posting, and for visiting Database Journal!

Bill