MDX - TopCount plus 'Other' or 'The Rest'

I have created an MDX query which calculates the TOP 10 ZipCodes (according to my Patient Stay measure) as such:

WITH
MEMBER [Discharge Date].[Y-M-D].[ Aggregation] AS 'AGGREGATE( EXISTING { [Current Month] } )', SOLVE_ORDER = 0

SELECT
NON EMPTY { [Measures].[Patient Stays] }
ON COLUMNS,

TOPCOUNT({ ORDER( HIERARCHIZE( { [Patient].[ByZipcode].[All].CHILDREN } ), ( [Measures].[Patient Stays] ), BDESC ) }, 10)
ON ROWS

FROM [Patient Stay]

WHERE ( [Discharge Date].[Y-M-D].[ Aggregation], [Facility].[ByAffiliation].CURRENTMEMBER, [Facility].[ByRegion].CURRENTMEMBER )

This query is used to populate a PerformancePoint 100% Stacked Bar chart. The client has asked that since this is a !00% based chart, we lump the rest of the zip codes into an "Other" field, such that there should be 11 values: one for each of the top 10, and an eleventh which is a sum of the remaining Zip Codes.

I am an extreme novice to MDX, but this doesn't souund like it should be impossible. Does anyone have any ideas or suggestions?

Solution

I'll do my best with untested code, so here goes:

WITH
MEMBER [Discharge Date].[Y-M-D].[ Aggregation] AS 'AGGREGATE( EXISTING { [Current Month] } )', SOLVE_ORDER = 0

SET [Top10ZipCodes] AS 
    (TOPCOUNT({ ORDER( HIERARCHIZE( { [Patient].[ByZipcode].[All].CHILDREN } ), ( [Measures].[Patient Stays] ), BDESC ) }, 10))

MEMBER [Patient].[ByZipCode].[OtherZipCodes] AS 
    (AGGREGATE({EXCEPT([Patient].[ByZipCode].Members, [Patient].[ByZipCode].[Top10ZipCodes])}))

SELECT
NON EMPTY { [Measures].[Patient Stays] }
ON COLUMNS,

{[Top10ZipCodes], [Patient].[ByZipCode].[OtherZipCodes]}
ON ROWS

FROM [Patient Stay]

WHERE ( [Discharge Date].[Y-M-D].[ Aggregation], [Facility].[ByAffiliation].CURRENTMEMBER, [Facility].[ByRegion].CURRENTMEMBER )

What this does is creates a set of your top 10 ZIP codes, and then aggregates (different than sum!!!) all the ZIP codes, with the exception of your top 10.

Also, if this is a common set (top 10 ZIP codes), you may want to make a set on the cube, where you can reuse it ad nauseum, without having to change every MDX query you have.

Cheers,
Eric