Create a month grouping

[renannog]

I need to create a group, always taking a block of 3 months and adding the billing.

Nov - Out - Set = 1000

Out - Set - Ag  = 5000

Set - Ag - Jul - 8000

I'm happy if someone can help me!!! 

[amitchandak]

@renannog , it better to use a rolling month measure

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

Rolling Months Formula: https://youtu.be/GS5O4G81fww