Extending, in the more general sense

Is there any possible method of adding functions to sealed classes?

I wrote a small function for drawing segments of circles (see here: http://kirupa.com/forum/showthread.php?p=2297429#post2297429) and was wanting to add it to the graphics Graphics object of display objects.

I wasn’t able to achieve this by prototyping methods because the Graphics class isn’t dynamic.

Is there any method of doing this?