MDX - Returning the value of a measure at a particular level

Question

I've got the following query which runs against the AdventureWorks 2008R2. It returns the [Internet Sales Amount] for the cities to which the following members belong
[Customer].[Customer Geography].[Customer].&[18702] and
[Customer].[Customer Geography].[Postal Code].&[2055]&[North Sydney]
with member MEASURES.[INTERNET SALES CITY] as
aggregate([Customer].[Customer Geography].CurrentMember, [Measures].[Internet Sales Amount])
select 
MEASURES.[INTERNET SALES CITY] on 0,
[Customer].[Customer Geography].City on 1
from
(SELECT {[Customer].[Customer Geography].[Customer].&[18702],[Customer].[Customer Geography].[Postal Code].&[2055]&[North Sydney]} ON COLUMNS  
from [Adventure Works] )
Result
[INTERNET SALES CITY]
Coffs Harbor $235,454.97
North Sydney $159,227.11
My question is how can I get the result in the following form?
[INTERNET SALES CITY]
$394,682.08
Thank you

Answer 1

Ok, looks like using a dynamic set solved this problem.
with
dynamic set [Selected Cities]
as [Customer].[Customer Geography].City
member MEASURES.[INTERNET SALES CITY]
as
AGGREGATE([Selected Cities], [Measures].[Internet Sales Amount])
select
MEASURES.[INTERNET SALES CITY]
on 0
from
(SELECT {[Customer].[Customer Geography].[Customer].&[18702],[Customer].[Customer Geography].[Postal Code].&[2055]&[North Sydney]}
ON COLUMNS 
from [Adventure Works] );