How to Get Cumulative Counts using Special Categories


Is there a way to create cumulative count in cubes???For ex if data is like,
Mnth Count
Jan 1
Feb 2
Mar 3

The cube should provide me the data like
Mnth Count Cum.Count
Jan 1 1
Feb 2 3
Mar 3 6

Is there a way to achieve this in the cubes??
I have read somewhere that this can be achieved using special categories in transformer??If so,please help me in achieving it.

Thanks in advanceā€¦