For years I have used Excel as an address book with one extra column per
year, in which I enter an 's' for a card I have sent, and an 'r' for a card I
have received. I have 5 extra columns labelled X0 -> X4 for years 2000 to
2004, which I then re-use for years 2005-2009.
I've now imported the Excel file into Outlook 2003 and I'm moving fields X0
to X4 into the Outlook supplied fields "referred by", and "User 1-4"
inclusive. This seemd easier than creating new fields, though this is also
possible.
When you want to update the fields, you can either import and export between
Outlook & Excel , or you can define an Outlook form which gives you direct
access to these supplied fields.
Good luck - it worked for me, though I'm still figuring out how to validate
the data as being only characters 's' and 'r' in the Outlook fields.