Insert with guid using detailsview

So I have a detailsview that I'm using to display and edit data.  I would also like to use it to insert a new record into the table.  The primary key for the table is a guid.  Obviously, the user cannot provide me with a guid, so I'll have to provide it myself. 
So my question is:  How, when, and where to I provide the guid to the detailsview or the sqldatasource?  Remember I'm new to this asp.net stuff.  :)
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