I've been working with a TreeView control to use it as a data-entry mechanism instead of a naviagation mechanism for a few weeks now. I finally found a solution. Its a bit of a hack, but it works flawlessly. Please see my blog entry on it:
http://adoguy.com/viewrant.aspx?id=2042
(If this has answered your question, please click on "Mark as Answer")
Thanks,
Shawn Wildermuth
C# MVP, MCSD, Speaker and Author
http://adoguy.com/silverlight
Silverlight Workshop
January 15-17, 2008 - Atlanta, GA
February 5-7, 2008 - Boston, MA
(Other locations available)
http://www.silverlight-tour.com