Powerview / Powerpivot: calculate marketshare

Hi all,

At the moment I am working with powerpivot and poweview to create an marketshare dashboard for my organization. All my data is structured in one single table with the following design:

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etc......

I would like to create a view in powerview where i see my marketshare tracked over the weeks with the product category as a filter. Is this at all possible?

Normaly I would use an regular pivot table with an calculated item and a slicer to accomplish this but the amount of data is to large for a regular pivot table.

Any help would be much appreciated!