If value in cell C is duplicate change value in cell B

gcjager 

Here's a simple way to do it, a way that does rely on adding a column. The formula compares each row in column B with the next, as well as each row in column D with the next....when both are the same, it returns a 0, otherwise, the original value.  See the attached spreadsheet for a working copy.

=IF(AND(B2=B3,D2=D3),0,B2)

A macro/VBA routine might be able to do this task without the additional column; I prefer an approach like the one I've shown because it retains your original data just in case there's any question.