I've got a spreadsheet with a list of alphanumeric values:

62:EF:62:EF:9C4A
62:EF:62:EF:B09B
62:EF:62:EF:A0F4
62:EF:62:EF:AF71
62:EF:62:EF:B309

I'm trying to find a way to insert a colon between the final four
characters, so that they are separated into two pairs so that the
outcome is:

62:EF:62:EF:9C:4A
62:EF:62:EF:B0:9B
62:EF:62:EF:A0:F4
62:EF:62:EF:AF:71
62:EF:62:EF:B3:09

I've used file/folder renaming utilities before that allow you to
insert or replace a value by counting so many spaces from the
beginning or the end of a value, but I don't know how to do this in
Excel. I also use the freeware ASAP utilities frequently, but don't
see a way to do this. Any suggestions?

Thanks!