Using a custom control

Ok I'm not exactly sure if this is the correct place to ask this, but here goes.

I am using a method call AddControl that takes two strings as arguments.  The first argument is the "Class Name" of a control, the second is some sort of license code for the control.

For Example, If I wanted to add a Calender, I wold call the function like this:

object obj = AddControl("MSCAL.Calendar", "")

This would add the Microsoft Calendar control and pass me back a pointer so I could access it's methods and properties.

Ok my question is this, I now extend the Calendar control by creating a new c# Control Library project.  I can compile and use this control by dragging it from the toolbox and placing it on a form, but I cannot get it to load using the method above.  I tried calling it by it's class name TestControl.TestControl, but that doesn't work.  I have tried using the GUID as the Class name, but that doesn't seem to work either. 

Any help would be appreciated.

 

John