Regarding EXCEL conditional format to check duplicate values, the operation steps are as follows:

1. First open the EXCEL table to be copied, and then insert an auxiliary column next to the copied column.

2. Then enter the formula = "a" in the auxiliary column &; B3, put down the formula. The letter A is added here to force the system to match through text. A needs double quotation marks in English mode.

3. Then select the auxiliary column and click Start-Conditional Format.

4. In the pop-up window, select Highlight Cell Rule-Duplicate Value.

5. Finally, click OK in the pop-up page, thus solving the problem of checking duplicate values in EXCEL conditional format.