Trick to convert roster export to draft class

[gnlmppvs]

So I thought I could use the M12 Editor, dump the entire roster to csv, then use Excel to whittle it down to X years pro, and that would give me a good baseline to create that year's draft class for whatever year. or so i thought

When i try to import that file as a draft class through the editor at the start of week 1 of a new franchise, it complains it's missing columns.
Is there a trick to get the columns right from an export? or a guide to follow?