We run a sports performance gym, and I want to create a chart to track member growth, by month, over the last 6 months or so. We group members under the Accounts module (e.g. a family of 4 contacts has 1 billing account).  

We do not have a "sales cycle" and do not do proposals so the Deals module with "Stages" is not applicable. Our revenue is purely recurring. Also, using it would require a lot of rework to our current setup.

All I want to do is make a chart of the running total of currently Active Accounts. If you were in the Accounts module viewing a filtered list, it would be the grand total of all records meeting the filter criteria. 

Does anyone have ideas on how this can be done? It seems like it should be absolutely simple, but I can only get partway there.