Growth figures within a report

[Markd78]

Hi all
Does anyone have any ideas how I can combat the following issue I am having?
I have been tasked with producing a crosstab report showing growth month on month for a 12 month rolling period. 
The idea is that I can show month on month how many active customers we have in any month for any year
The problem I have is that there is no data item that I can use for "active customers" so I dont have anything I can use to put a date against. 
So far I have managed to produce a report for all new members in a given year, by month with a percentage growth from one month to the next.
Without an "active customer" data item I dont know if this is even possible?
My thought was to represent each calendar month using a query per month but as I need to do the previous months calculation as well this will become a report with 24 queries  :-\
Does anyone have any ideas on this at all?
Have I given enough information?
Kind regards

[gpollock]

You're being tasked with showing a month-by-month report for data that isn't even in Cognos?  I don't think that's ever happened before. ;D

Can you use a fact like net sales?  This question sounds more like dealing with people than dealing with Report Studio.  Regardless, if you give them something and get a clear definition of what growth is, you can start the conversation from there.

Is there something from a technical standpoint you're trying to figure out how to do?