You need to change the MessageClass on the existing items to point to your
new form's class. See
http://www.outlookcode.com/d/newdefaultform.htm#convert for several tools
and scripts to accomplish this.

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Sue Mosher, Outlook MVP
Author of
Microsoft Outlook Programming - Jumpstart for
Administrators, Power Users, and Developers
http://www.outlookcode.com/jumpstart.aspx
>I have a database of some 600 contacts, and I want to add the same extra
> fields to ALL of them. I can see how to do it one by one, but how can I
> get
> ALL contacts to use the altered form?