Extending the Button Class

I have an AS file named MovieClipTLnd which I created to add a property to the MovieClip class, plus a function to trace the current value of the property I added.
I works out just fine.
But when I do the same trying to extend the Button Class, it won’t work.

check the last lines of this LiveDoc, a few days ago someone posted a comment regarding this problem

[color=#800080]http://livedocs.macromedia.com/flash/mx2004/main_7_2/00001211.html#4716791[/color]

I know there are some workarounds for this problem… like embedding the button into movieclips and assigning properties as objects, but I need to know if it’s possible to Extend the Built-in Button class itself just like it can be done with the MovieClip Class.