Follow up: I figured out why your duplicate value rule wasn't working the way that you wanted it to. When you selected the Range for which data values you wanted it to find a duplicate value, it searched EVERYWHERE in the range. So for invoice number 63000 where the 48.84 is, the reason it is highlighted is because it also found this data value with invoice number 64482. If you wanted to use the duplicate values, you would have to use a new conditional format for each line.