To get this cumulative data in a report you will need to do a few things.
You will need to take a snapshot of the data and summarize it into some table, then use that table to be compared to a month or week table (depending on how you want to group things.
Basically do do this without any script it would take a decent amount of work to get the data flowing the right way.
Do you have more info about your use case or an example report that you are currently using?