How to add a dimension to aggr rolling expression

[#1]

Hi

I have this expression

=IF(PeriodCounter >=24, sum(aggr(rangesum(above(total sum({<Month=, Year=, PeriodCounter=>} Belopp),0,12)),PeriodCounter))

I´t gives me the correct Rolling 12 sum for each row. Now I would like to add a dimension (Class) to the table. When I add the Class dimension in the expression, like this

=IF(PeriodCounter >=24, sum(aggr(rangesum(above(total sum({<Month=, Year=, PeriodCounter=>} Belopp),0,12)),PeriodCounter, Class))

Then it calculate the Rolling wrong. There are 3 diffrent values in the Class dimension. I want it to calculate the Rolling for each class value separately.

Any suggestions?