Outlook doesn't have any concept of subcategories unless you've added a
keywords field to do that, along with whatever programming logic you want it
to have.

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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 wonder if it is possible to add the "Sub_Category" combo box at the
>Outlook default Contact form. At present when openning the Contact form I
>can see the combo box and I can assign Category to a contact, but I need to
>further categorize the contact into Sub-Category based on the category item
>selected. Thanks