I have a Measure.TransactionValue and also a Date.Month Dim and a
Subscriber Dim

I want to do a Count of months since first transaction date by
Subscriber

i..e
Subscriber | Month | Measure.TransactionValue |
Measure.MonthsSinceFirstTran
1 | 201002 | 0 | 0
1 | 201003 | 100 | 1
1 | 201004 | 200 | 2
1 | 201005 | 300 | 3
1 | 201006 | 0 | 4
1 | 201007 | 50 5

Make sense?

Any help would be greatly appreciated.