Time Line Recurrence Formula

Hi all,
I’m using the new time line category but I’ve a problem with the recurrence formula.
FORMULA: Cumulated Costs=”Total Cost:Month[THIS]+Cumulated Costs:Month[PREV]”

In this way QM calculates the progression also in January of the next year but, as it’s not a cash flow but a sum of annual costs, it would stop in december.

Solutions?

Thank you so much.