To create a new instance of a custom form programmatically, use the Add
method on the target folder's Items collection. If it's a message form, you
can use the Drafts folder as the target. If the form is published in a public
folder, you can create items using the form only in that folder.

If the target is a default folder, you can use the
Namespace.GetDefaultFolder method to return it as a MAPIFolder object.
Otherwise, you can use the code at
http://www.outlookcode.com/d/code/getfolder.htm to walk the folder hierarchy
and return the MAPIFolder corresponding to a given path string.
--
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