I have a spread sheet with a thousand rows. These rows were numbered sequentially by part number. However, over the years people have deleted and added many rows (and there numbers). Is there a way to find out which part numbers are missing?

How about sorting the list, so you can scan and see where the gaps in part numbers are? If the parts are sequential (part 1, part 2, etc), you can put a formula in the adjacent column to show a flag if the part number is not equal to the previous part number plus 1.