Multiple columns within matrix with zero values - Need to exclude zero values without impact

Hello there datadelta ! Try unpivoting your columns, like so:

Select your "Store" column and the "Unpivot other columns" option in order to have only three columns: one with the name of the store, another with the product sold and the last with the amount. With this you can freely apply the formula above!

Hope this answer solves your problem! If you need any additional help please tag me in your reply.
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Thanks!

Best regards,
Gonçalo Geraldes