"Phil" <Phil @discussions.microsoft.com wrote...
I have two data sources. One has the old part number and the other has the
new part number. I need to compare the two lists and build a third with the
correct part numbers to upload into our system.

If the only difference is that one has its first hyphen where the other has
its first space, try

"4-ABC-SS"=SUBSTITUTE("4 ABC-SS"," ","-",1)