Aggregate function in Expression

[#1]

Hello,

Please take a look at the formula bellow.

Can anybody say why it does not work?

IF (GetSelectedCount(Year)=1 and Month(%Date)=Aggr(Max({1}Month(%Date)),Year),Sum(qty))

What I am trying to do is to create column in table that will summarize
actuals when specific year selected and Month equal to the highest Month in this year.

If the conditions are not satisfied do nothing.

But when I put this formula in expression I get no result.

I also tried to put Aggr(Max({1}Month(%Date)),Year) as variable
but it is still does not work.

Please anybody help