Outlook views show only items in a single folder (except for mail search
folders in Outlook 2003). You might try using Advanced Find to search items
for the project.

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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 would like to create a view that combines calendar and task items that I
> can filter using a custom project field I have already created. How do I
> do
> that?