Set Analysis

[danny4202001]

Hello  Friends,

How to add vNextMonthYYYYMM more months to this where to add +1 month +2 months in the below expression its erroring out 

sum({$<CancelDateYearMonthMM_OO={"=$(vNextMonthYYYYMM)"}, %ShipDate=, %ShipDateMonth=,
%ShipDateYear=, %ShipDateDay=, %CancelDate=, %CancelDateDay=, %CancelDateMonth=, %CancelDateYear=,
OrderDate_OO=, OrderDateDay_OO=, OrderDateMonth_OO=, OrderDateYear_OO=>} Quantity*SELLING_PRICE)

THANKS,

D