There's no built-in way to do this. See http://www.outlookcode.com/d/database.htm for tools and techniques that might help.

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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
>I have "Vendors" in Outlook, and "Customers"
> I also keep duplicate records for "Vendors" and "Customers" in my Access
> Database.
> How can I enter them in one place and have it updsate Outlook and Access?