How would I populate future months

Hi Tripb44 ,

You can calculate the rolling avg 3 month like this:

3 MO avg = 
CALCULATE(
    AVERAGEX (
        VALUES ( 'Date'[Calendar Year Month] ),
        [Sales Amount]),
    DATESINPERIOD('Date'[Date], MAX ( 'Date'[Date] ), -3, MONTH )
)

Processing of data for future months, you can read this case for reference:Solved: Rolling Average for Future Months - Microsoft Power BI Community

If the problem is still not resolved, please provide detailed error information and let me know immediately. Looking forward to your reply.

Best Regards,
Henry

If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.