How to show % of Parent Row GRAND Total in a Pivot Table / Chart

Hi,

I need to create a Pivot Table that shows values as % of Parent Row Grand Total. Currently Excel supports only to show % of Parent Row Total 

Below an example.

I have a pivot with 2 levels in the rows and 1 level in the columns.

In the rows I have the sales of different products by week (level 1) and by product type (level 2)

In the columns I have the feedback on the sales (negative, positive, none)

I can build a pivot that shows the items on each cell as % of the Parent row total (e.g. in Week42, Card1F's 67 negatives as 38% of parent row total 175, Card1F's 143 positives as 42% of parent row total 343 etc.).

I need to show values as percentage of parent row Grand Total (e.g. in Week42, Card1F's 67 negatives as 12% of parent row grand total 574, Card1F's 143 positives as 25% of parent row grand total 574 etc.).

I could not find a way to perform the requested task the straight way. Is there a way to do it using some workaround?

Thank you in advance.