globalToLocal() Problem

i am trying out with globalToLocal function and I realise something and that is if I put two movies into another movie clip, it wont work well.
Let’s say if there are aMC and bMC on the stage. when the actionscript is something like…
x = new Object();
x.x = aMC._x;
x.y = aMC._y;
_root.bMC.globalToLocal(x);

and i move the aMC onto bMC and place aMC onto bMC’s starting corner, it will appear as 0,0 as the coordinates during runtime.

however now, if i put both aMC and bMC together into another movie called cMC and do the samething, when aMC is moved onto bMC’s starting corner, it doesnt appear the coordinates as 0,0 anymore. It will show the coordinates of the cMC’s I guess since it appear to be some big negative numbers when I try.
How can I get 0,0 coordinates, which is what I needed when aMC is placed onto bMC’s starting point even though both are in cMC?

I know its a little perplexing and so I have made a .fla just incase u dont get what I mean. the .fla will roughly give you what I am trying to ask.

Thanks!