How to create Accumulative Count of active member within 3 months ?

[jim_chan]

Dear all, 

I have a requirement from my client.  i have attached the sample qvw file and excel data for your reference. 

Basically, these are the requirements:

1) accumulative count

2) accumulative count that include members who are actively(with sales) within 3 months. 

Formula at the front end i have used is:

RangeSum(above(sum(aggr(count (distinct MemberID),MemberID )), 0,RowNo()))

However, thats not the result i am looking for:

The expected result should be only populate out/accumulate count on active members only. From Jun onwards - active member should have only left 2, instead of 4. As the active members ID within the 3 month from Jun - is only 2 - ID 1001, 1002. 

[jim_chan]

hi there?? 

anyone?? can help???

Rgds

Jim