MONITORING BALANCE OF LAPSED CUSTOMER BY MONTH

Hello,

I'm stuck on a basic dashboard I'd like to create... I'd like to show for cumulative balance lapsed customer each month :

I want to display the number of lapsed customers in 2020 (January 2020,February 2020, etc)

for example:

1. In January 2020 the figures shown are the number of customers who have not made a purchase in the last 12 months (January - December 2019) but made a purchase in the previous 12 months (January-December 2018).

2. Then in February 2020 the figures shown are the number of customers who have not made a purchase in the last 12 months (February 2019 - January 2020) but made a purchase in the previous 12 months (February 2018-January 2019).

and so on for figures in Mar 2020, Apr 2020, etc.

I've started doing it on the Sample data but I'm having trouble with it and I've read the numerous threads that address this topic but to me they never really address the very issue I'm having.

Any help ?

Thanks