Hi

I am trying to change the aggregation on a dimension structured as
below.

All
-> Group 1
-> Item 1
-> Item 2
-> Group 2
-> Item 2
-> Item 3

I need the All level to calculate the distinct sum of items so that
Item 2 is only included once.

I have tried the following MDX in the All Member Formula field but have
not been able to get the correct result.

sum(distinct({[Dimension].[Item Level].Members}))

Any help would be appreciated

Thanks
Gavin.