Adding Property to ActiveX Plugin for Powerpoint

I am trying to figure out properties and how Powerpoint and ActiveX plugins communicate.  I am having problems getting properties to show up inside Powerpoint, and am having a very difficult time finding documentation.  I downloaded a sample (control123) from the web, and tried to add a new string property "TestString" and it doesn't show up in Powerpoint. (see attached project).  Do you know what's wrong?  I did exactly what the MS documentation online says to use the "Add Property Wizard" (http://msdn.microsoft.com/en-us/library/khbc069h.aspx)  I am using Office 2010 and Visual Studio 2010.

My sample project is at: http://www.blainebell.org/contral123.tar

Thanks for your help.

Blaine