How to create an indexing column in table visualization

Hi guys,

I have two tables. One table contains all users, and the other is a subset sample.

I want to create a table visualisation that has the brand_category, the number of distinct hashed_emails in table 1 and the index. The index is calculated by (%GT of distinct hashed_emails in table 1) / (%GT of distinct hashed_emails in table 2) where table 1 is my index. This basically just tells me if a particular brand is over-indexing in my sample compared to the population.

I also want all filters and slicers on the page to affect this table.

I can easily create a table where I have the brand category, and the %GT from both tables, but I'm unable to do the calculation where I divide one by the other.

Can anybody help?

Cheers