Spend Groups based on dynamic month selection

DAX DAX Calculations
4

Check out the formula below

Months Purchased In 12 months back = // Number of months that each particular client purchased in within the last 12 months from the date selected.
VAR MonthlySales = 
CALCULATETABLE(
    SUMMARIZE( 'CALENDAR', 'CALENDAR'[Month & Year], "SalesAmt", [Total Net Sales] ),
        DATESINPERIOD( 'CALENDAR'[Date], MAX( 'CALENDAR'[Date] ), -1, YEAR ) )
RETURN 
COUNTROWS(
    FILTER( MonthlySales, [SalesAmt] > 0 ) )

This came this forum thread.

Chrs