Is there a way to use conditional formatting to highlight a range of cells that repeat the same exact values throughout an entire work sheet?

Example:
12121 - Highlight
23232
12123
34343
12121 - Highlight
13232
56565
12121 - Highlight

This is just a quick example of what I wish to accomplish. The values must be exactly the same in each column and as an FYI some cells may be blank.

Thanks!