Outlook doesn't have any concept of subcategories. All categories are
created equal.
You can enforce category selection through a custom form. See
http://www.slipstick.com/dev/olforms/reqcat.htm for more an example.

Signature
Sue Mosher, Outlook MVP
Outlook and Exchange solutions at http://www.slipstick.com
Author of
Microsoft Outlook Programming - Jumpstart for
Administrators, Power Users, and Developers
http://www.outlookcode.com/jumpstart.aspx
> Hello,
>
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>
> Ruan