As inspired and hacked by Karim check out:
'Now that you have the DLL we can now open Visual Studio and start a new project. For really hacking into Expression Blend so that our...'
rest at:
http://hackingsilverlight.blogspot.com/2008/07/hacking-expression-blend.html
I started a code plex project on code plex... dah... that has a Silverlight control library solution with items from the forth coming book. right now I only did unit tests for 7 of the controls namely multi panel and some of the other panels and then mouse wheel support and browser history...
read the rest at:
http://hackingsilverlight.blogspot.com/2008/06/control-library-on-codeplex.html