Sum of sales from 4 months ago to 1 month ago

[ZaheenHamidani]

I need to sum the sales from 4 months ago to 1 month ago taking as reference the filtered month, it means:

October 2020: 4

November 2020: 6

December 2020: 3

January 2021: 7

February 2021: 2

The result should be:

January = 13 (Oct + Nov + Dec)

February = 16 (Nov + Dec + Jan)

I tried using this: 

But it gives another result.

Thanks to help.

[amitchandak · Accepted solution]

@ZaheenHamidani , Try with a date table like given example

Rolling 3 before 1 = CALCULATE(sum(Sales[Sales Amount]),DATESINPERIOD('Date'[Date ],eomonth(MAX('Date'[Date]),-1),-3,MONTH))