Hi,

you can use the conditional formatting to highlight duplicate values.
If the duplication requires testing of values in more than one column, you can create a test string by concatenating cell values.

to try this, put "C" in cell a1, "1" in cell b1, and "=a1 & b1" in cell c1.

you can use this to create the test value from which you can use the find duplicates/conditional formatting features