Jon,
That's the thing, there is no easy way to do this with Windows controls.
The logic of the components and the parts is all self contained. This is
very different from Windows Presentation Foundation, where you can actually
see the different components of composite controls, usually (the radio
button would have a text element, for example).
For windows controls, you are going to have to redraw the whole control
yourself.
The unmanaged thremes API (this is a link to the starting point):
http://msdn2.microsoft.com/en-us/library/ms649785.aspx
Might help you a little bit, in that you can tell it to draw certain
parts of the control in certain states (and it does separate some of the
parts out for windows controls) but it's still going to entail a great deal
of work.