set analisys

[Anonymous]

Dear all,

I'm using the following expression, but I aim to know how it works. Let me add more detail: in my intention,

I would sum all the purchase values till August (MY_MONTH) or other selected month

aggr(sum({<PURCH_MONTH={"<= $(=only(MY_MONTH))"}>} PURCHASE_VALUE),MY_YEAR, MY_SUPPLIER)

It seems correct, because I get the required values.

Now, I need to  calculate another value but for PURCH_MONTH < MY_MONTH.

I was convinced that I could do it changing the condition  <PURCH_MONTH= {" < $(=only(MY_MONTH))......

but it doesn't work.

Does anyone know what I'm doing wrong ?

Thanks in advance

stefan