Highlight different values based on duplicate in another column

Hi,

I would like to highlight cells that are different based on duplicate values in another cell.
e.g.
Nr - Name - buy - sell
1 - Power supply - 15 - 20
2 - Power supply - 10 - 20
3 - Cola - 14 - 10
4 - Cola - 14 - 10
5 - Milk - 13 - 1
6 - Milk - 13 - 2
7 - Pringles - 15 - 10

I want 15 and/or 10 to be highlighted, since "Power supply" is the same, but the "buy" is different. Same for 1 and 2 for "Milk". I have around 20 columns I would like to check.

Please refer to the file attached - rows 7 and 8. I have manually coloured to red the values that differ. Rows 2 and 10 are also duplicates.

Thanks,