Function to comparing data on Separate Excel Worksheet tabs

Guys,

I am trying to compare two sets of data held on separate excel worksheets.

Worksheet 1 has UAT data, worksheet 2 has PROD data. I want to use an excel function to help verify the information held in both large worksheets tie up.

I have been trying to use the CONCATENATE function to assign a Primary Key. Any other ideas, really need it for a project. You will be saving my life!

Thanks,

Melvin