Import contacts from Excel to Outlook with custom categories

A client of mine was using an old version of Goldmine to manage their contacts and are going to transition to just use Outlook. I was able to export all of the contacts into a CSV in Excel. I then cleaned them up to have the columns match the field mapping in Outlook. Importing them went well but I am now being told that they want them categorized in a special way. For example, in Goldmine users may have been a member of "Attorney" as well as "Legal Attorney". These attributes were listed in a columns called Key1 and Key2 which don't map to an existing field for Outlook. I want to set up categories within Outlook to match the categories they had and somehow have them automatically become part of these categories during import. I am not sure if this is possible or not but any options you can offer would be helpful as opposed to manually editing all 4,000+ contacts. Thanks in advance!