"Aggr" function and set analysis questions

[#1]

Hi all, I need to solve the following problem:

- in a table I have the "#USIM" values on a daily base. I calculate the average between the sum of #USIM at monthstart and at monthend through the expression:

((

sum({<[Month]=, [Day]=, [Reference Date]={'$(=max([Data riferimento]))'}>} [#USIM]

)

+

sum

({<[Month]=, [Day]=, [Reference Date]={'$(=monthstart(max([Data riferimento])))'}>} [#USIM]))/2

))

Now I need to represent this expression on a monthly trend and here I experience the issue. Do I have I to use the "Aggr" function? How can i combine the "Aggr" function with the set analysis?

Thanks in advance for your help

Daniele