qlik sense

[Ravi1]

i have two tables master and fact these tables are linked using s.no values from 1 to 6

I need the sum(amount) for S.no = 4 on selecting S.no= 6

i used "=If([S.No]=6,Sum({<[S.No]={4},Year={"$(=Max(Year)-1)"},MonthNo={"$(=Max(MonthNo))"}>}Amount),0)" 

This didn't work

need help please