ActionScript 3.0 :: ReferenceError: Error #1056: Cannot Create Property

I create a shape, and I want to move it with a ENTER_FRAME event, like this:

public function makeShape(){
var myShape=new Shape();
addChild(myShape);

[code]....

But what if I want to pass a variable with my shape to the event function. Say my shape has a no or a name or anything like a data; so I rewrite the code;

public function makeShape(){
var myShape=new Shape();
myShape.thisShapesNo=50;

[code]....

See the extra workload.. And the other way (and I've never tried) is to write your own event function where you can pass variables.. I guess something like this:

myShape.addEventListener(Event.ENTER_FRAME, moveMyShape, 50 );

So it seems like this is another extra workload for the code.And so here is my question: How can I add a you-name-it property to any thing I've created in AS3?