Conditonal formatting a duplicate value with mutiple criteria

Need help on formatiing a cell, e.g. change color to RED, in the event the value is a duplicate.
To make it clear, I need to show that if the Serial Number of a product just entered is a duplicate and should change color when a combination of conditions is true. i.e. if a "part number" AND the currently entered "serial number" already exist, the entered serial numbers should change color.

Thanks in advance

Any chance of some sample data?

Originally Posted by FDibbins

Hi and welcome to the forum

If I understand you correctly...

1. highlight the range you want to apply the conditional formatting to
2. on the home tab, styles, select CF
3. select new rule, select "format only unique or duplicate value"
4. Select Duplicate

Thank you for your suggestions. I had tried this before, but it doesn't solve the problem. That's is why I post this on the forum. Here is a sample file. Maybe you could come up with a better idea. The file is modified for forum purpose.