Set Analysis with aggregate

[#1]

I am using an aggregation function in which i want to include set analysis for the previous year and am struggling a little bit. the expression which does not work is

=-sum( {$<[Year-RCV] = {$(=Min([Year-RCV])-1)}>} aggr([Transit Time] >= ([Receipt Date] - [Ship Date]),[Doc. Number]))

am using the same set analysis to count in another expression and it works. the working expression is

=count({$<[Year-RCV] = {$(=Min([Year-RCV])-1)}>} distinct [Doc. Number])