Power BI Running Total Cumulative Value for 12mth periods

[MNH]

Hi, I am new to PowerBI and have been getting to grips with how DAX works.  I've hit the wall with trying to get a running total cumulative value that .  Below shows what I am trying to achieve.  I have a simple table with 2 columns - Period and Period Count.  I can build a cumulative total in DAX that increments each month and continue on for all months (Column callced Cumulative Count DAX below).  However, what I'm after is for the cumulative value in a period to be the sum of the previous 12 months.  For example, in Period = 202008 return a sum of this month plus the previous 11 months.  Then do the same for 202009 and so on.  I tried setting a start date and end date for each Period so that, for example, 202008 has start date of 1/09/2019 and end date of 31/08/2020 in order to CALULATE SUMX of counts between a date range involving start date and end date but don't get what I'm after.  I've tried using DATESINPERIOD and RELATEDTABLE in various formulas but drawn a blank.  All I get is a cumulative total for all months or the value for just the month.  Any ideas whether what I am trying to achieve is even possible?

[amitchandak]

@MNH , You can try rolling 12

Rolling 12 = CALCULATE(sum(Sales[Sales Amount]),DATESINPERIOD('Date'[Date],MAX('Date'[Date]),-12,MONTH))

if need, create a date from the month year

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

[MNH]

Thanks for taking the time to look.  I've watched the YouTube link and attempted to apply the formula to my dataset.  However, I get different results to expected.

This is one of the measures

Cumulative attempt 1 = CALCULATE(SUMX(RELATEDTABLE('Data'),[Count]),FILTER(('Data'),'Data'[Date]>=[Date minus Year] && 'Data'[Date] <= 'Data'[Date]))

This measure is from your example, which I can see working perfectly in your YouTube clip but doesn't on my dataset.  What could be going wrong?

Cumulative attempt 2 = CALCULATE(SUM('Data'[Count]),DATESINPERIOD('Data'[Date],MAX('Data'[Date]),-12,MONTH))