I currently have a spreadsheet with column N listing usernames. Column N already has a formula which is =CONCATENATE(LEFT(B2,1),D:D). I would like to add to this formula some way to highlight that cell red if duplicate is found.
The problem is that the formula is filled down to 8459437239 rows. When I use the conditional formatting tool, it highlights those rows which have a formula but are empty. How can I keep them from getting highlighted until actual data is entered?