Calculate last 4 months in each row

[JoshLeslie_07]

I just want to Calculate last 4 months in each row in Straight table , this is my first time to use QlikView Please help me

 My Sample Data.

here is exactly what I want.

but my output is wrong  screenshot below.

My Expression that I used so far , it's same result.

Max( aggr( rangesum( below( sum(Sales),0,4) ),Month))

Max(Aggr(RangeSum(Below(Sum({<Month, [MonthYear], MonthYear, Year>}Sales), 0, 4)), [MonthYear]))

Max( aggr( rangesum( below( sum( {$<MonthYear>} Sales),0,4) ),MonthYear))