Highlight Unmentioned Numbers

Oli_Kirrage There are 2 scenarios in the attached workbook:

1. You want if a number appears for the first time, it is highlighted but then if it reappears, both the cell of 1st occurrence and nth occurrence do not have any highlight: use the conditional formatting rule in Column A (use Countif(range,A1)=1 where the range should be an absolute range and cover as many cells as you could expect for your data range)

2. You want the highlight on the 1st occurrence remains but any nth occurrence does not any highlight: use the conditional formatting rule in column B (use column C as a helper column which could be hidden where the range for each cell in column C is a running range)

Note that cell A15 and B15 are test cases of a number already mentioned previously to see how the conditional formatting rules in each scenario differ.