Hi Henrique,
Sorry, but it seems like I'm stuck. I add the Sales but as expected no GROUP BY is done 
How to specify in an Attribute View the way how data is aggregated? I thought I can specify some JOINS and some Calculated Columns but somehow I missing the specifics how to do it the way you suggested.
Would you mind to give me a specific hint where I could select in the Attribute View your mentioned functionality? I mean I can then proceed by my own IF I would have an idea 
roland