Cumulative sum of values

Hi,

We usually use tssum to sum up values across time series.

Any idea on how we can cum sum across other hierarchies?

Example, I have a measure called store count which is at grade level and contains the store count by each grade.

A 20

B 10

C 15

I need a picklist measure which contains the cum sum of store counts, so the values in picklist should be 20,30,45 and so on.

Regards

Anusha Ramanan