Converting a movieclip to bitmap data (AS3)

Question

Hi,
Just been gradually switching over to AS3, and I've hit a
problem and its doing my nut in because I can't find a way to get
it to work.
Basically I want to take a portion of a movieclip and convert
it into bitmap data into another movieclip.
I know the basis would be something like:
var b:BitmapData=new BitmapData(100,100,false);
var bm:Bitmap=new Bitmap(b);
mymc.addChild(bm);
But I can't work out how to get that to pick up the movieclip
that I'm trying to extract from.
Hayyyulp.
The link below is the kind of method I want, but because this
is drawn at real time it would cause the area to expand with the
movie clip, when all i want is to extract a portion and place it as
a surface texture. (draw on the box on the right hand side)
http://www.visitmyworld.co.uk/body.swf
Also, I don't really think it necessary to update in
realtime, that and id assume generating the bitmap area in real
time would cause major slowdown issues. If anybody has any
different solutions to what I propose then advice welcome.
The reason id want a bitmap is that data id want to project
could be complex layers, ie- items can be dragged on rather than
just being drawn on.
Cheers,
Adam

Answer 1

And also, whilst we're at it, I seem to have hit a bit of
trouble with understanding to call a parent function
ie - in AS2 you would put:
_parent.myfunction()
Any ideas?.