We have a list of computers in an excel table, a few thousand. Most are named in the format of <3digit office code> - . For example, NYC-1234567. Sometimes, when machines get re-imaged, the techs will add a few digits to the end, since they don't want to delete the machine from the domain (or don't have the rights), so for example, NYC-1234567b or NYC-1234567-2
We also have some machines that might have been moved to another office, for example, if moved to LA, it might become LAX-1234567.
I need to "get rid" of duplicates in our spreadsheet to clean up licensing. I have played a bit with conditional formatting. I see I can set a formula for cell A2 conditional formatting of =COUNTIF(A:A,A2)>1 which will trigger on any duplicates. But how would I compare just the serial numbers, characters 4-11? I am at a bit of a loss. I'm not much of an Excel person.