Dates Between Dates Diff Tables

Hi, 

Is there a way to compare dates between two tables, and say 

if "TRANS_DT" is less than "Effective Date" in one row, but greater than "Effective Date" in the previous row, use "Grade" for that "RANS_DT" 

So for the screenshots below, since the "TRANS_DT" for the first row is 12/29/2019, and the "Effective Date" in row 3 of the second screenshot is 12/19/2019, row 4 is 6/1/2020, the row output for the formula would be "3"...

Please let me know if this question does not make sense...

Thank you!
Sarah