Display it in a table view and fill in the values with in-cell editing.
Or fill in the value on the All Fields page of each item.
Or create a custom form and apply it to all items. See http://www.outlookcode.com/d/contactform.htm and http://www.outlookcode.com/d/newdefaultform.htm

Signature
Sue Mosher, Outlook MVP
Author of Configuring Microsoft Outlook 2003
http://www.turtleflock.com/olconfig/index.htm
and Microsoft Outlook Programming - Jumpstart for
Administrators, Power Users, and Developers
http://www.outlookcode.com/jumpstart.aspx
> How to I add a User defined field to all contacts in a folder?