DAX Forecast Help (see attachment)

hi, Anonymous

After my test, if remaining minths Oct/Noc/Dec is the rest months of the year? you may try this formula as below:

new forecast = 
IF (
    MAX ( Table2[Month] ) >= MONTH ( TODAY () ),
    DIVIDE (
        CALCULATE (
            [Variance],
            ALL ( Table2[Month Name], Table2[Month] ),
            Table2[Month] < MONTH ( TODAY () )
        ),
        12 - MONTH ( TODAY () )
            + 1
    )
)

Result:

If you think about the year, you could create a year column and add the condition to the formula 

new forecast = 
IF (
    MAX ( Table2[Month] ) >= MONTH ( TODAY () )&& MAX ( Table2[Year] ) = Year ( TODAY () ),
    DIVIDE (
        CALCULATE (
            [Variance],
            ALL ( Table2[Month Name], Table2[Month] ),
            Table2[Month] < MONTH ( TODAY () ) && Table2[Year] = Year( TODAY () ) 
        ),
        12 - MONTH ( TODAY () )
            + 1
    )
)

 here is pbix file, please try it.

https://www.dropbox.com/s/pj2x49x98umrle8/DAX%20Forecast%20Help%20%28see%20attachment%29.pbix?dl=0

Best Regards,

Lin