I am not sure I understand your reply, as I posted the following in addition to the workbook: "I have a set of data with 302,000 rows that has one column that contains contract numbers, which can be alphanumeric and limited to 20 characters. I am importing this data into another system and cannot have duplicates. I have identified the duplicates, which total 1,276 out of the total of 302,000. I need a way to add a unique character at the end of each duplicate, which begins with the letter D, for duplicate, followed by 1 for the first duplicate, 2 for the second, etc.. I am attaching an example workbook of the data and what I want it to reflect for the duplicate values as an example. I would appreciate any help/advice anyone has."