Last 4 Months Accumulate value

[BrandonN]

Hello,

Need help on the accumulate last 4 completed month on expression, tried several ways not working need some help 🙂 
Expected output as below & attached QVF.

[justISO · Accepted solution]

if(YearMonth=max(total YearMonth),0, RangeSum(above(sum({$<YearMonth={"<=$(=Date(Addmonths(max(YearMonth),-1)))>=$(=Date(Addmonths(max(YearMonth),-4)))"}>} Value) ,0,4)) )

?

[BrandonN]

Thanks!