Hi @Gust ,
I've assigned parameters to the filters (button bars in my example) to capture the period selection on each table. Parameters were called FilterA and FilterB.
Then I've created 4 calculations for FilterA_col1, FilterA_col2, FilterB_col1, and FilterB_col2. Their expressions are very similar, Here is the expression for FilterA_col1:

Then I calculated the ratio between FilterA_col1 and FilterB_col1 and called it "Col1 Ratio", and then did the same for col2. This is the expression for "Col1 Ratio":

This is the result:

I hope this is what you wanted.