Hi. I'm a beginner of Tableau, I want to create a set which only contains the different values in dimension A and dimension B

here is my case: I'm a online marketing, so I export my CPC advertising keyword reports from Google, the data sources include "keyword report week 1" and "keyword report week 2"

and in both reports there is a dimension called "keywords"

I want to create a sheet in tableau that can show me the new keywords performance. The "new keywords " are the keywords we added during week 2, so these keywords only included in the week 2 report and not included in week 1 report.

My idea is create a set called "new keywords" and make it only include the new keywords, but I don't know how to make the set calculation,

Anyone can help me?

Thanks