I'm trying to track a small set of part numbers, 13 different parts. 10 of the 13 parts have serial numbers and I have my table to not allow duplicates. Works fine for the 10 parts. So for the 3 parts that don't have a serial number I want to make a serial number. Something like NM-0001 and for every time one of these parts are entered I would like it to automatically update to the next number. Ex - NM-0002 and so on. I cant figure out how to find the last number entered.