Future Dates

[Zara]

Afternoon all,

Have a report where the user will go in and select any year month and i want to do a count of any sales from that month and the subsequent 3 months only from that date. 

I've tried to replicate in the picture below

So if the user selected - 

Jan 2020 - I would expect the sum to be  166

Feb 2020 - i would expect the sum to be 191

March 2020 - i would expect the sum to be 172

Anyone have any ideas what i would need to put within my set analysis to be able to achieve this please.

Thank you in advance, i love the monthsago field, i suppose i'm looking for the opposite.

Thanks

[Anil_Babu_Samineni]

Perhaps this?

Sum(Aggr(If(GetselectedCount(SalesYearMonth)>1, Sum({<SalesYearMonth={">=$(=Max()SalesYearMonth)<=$(=AddMonths(Max(SalesYearMonth),3))"}>}SumSales), Sum(SumSales)), SalesYearMonth))