Issue with counting of members in a level

[dsg1]

Hi friends

I need to display the count of the members for the lowest level of the hierarchy (rows) along with the members (column) in a crosstab. The display will be as shown below.

           Children 1         Children 2    Parent
# stores             7                   8         15

The Location and the childrens are derived with the following expressions:

Parent  -> ?prompt?
children ( Parent -> ?prompt? )

I am facing issues while dynamically deriving the count for the lowest level here in the crosstab.

If I am using a list, the count can be derived using the expression:
count(1 within set descendants (#prompt('Parameter1','memberuniquename')#,[FINANCIAL].[LOCATION].[LOCATION].[lowerst_level])) but this expression is not working in crosstab.

Any pointers or help would be very much helpful.

Thanks
dsg