Detect A-Attach B-Release B-Attach to C ?

Ok here's something that sounds simple.

I have mc A moving slowly across the screen.
I would like to detect it's position x and y, and then at a certain coordinate(let's say x= 200 and y=300) attach mc B(which is just floating around) to attach itself to and follow mc A movement.
And then at some point attach mc B to attach itself to another mc(C).

Is it also possible to attach mc B to a certain pixel (xy) on mc A (or C).

Any ideas

Cheers

Trinitee

- maybe it could work something like:
this.onEnterFrame = function(){
if (A._x == 200 && A._y == 300){
B._x = A._x-50 // or whatever distance you want it to be from A's._x
B._y = A._y-50 // or + 50 or however far away it should be
}
}
//if you want a specific point to attach maybe you put another instance name inside of A and tell B._x to = A.instanceName._x;