Root trouble

I know there are many posts about root and I have looked at them but I have not been able to fix my problem with them.

On my top timeline (Scene 1), I declare…


var callRate:Number = 0.5;

I add a movie clip, S1, to the stage using addChild(S1). In S1 I declare…


var s1CallRate:Number;

How do I set the value of s1CallRate to 0.5 by referencing callRate?

NOTE: I have tried referencing callRate from within S1 in a trace function. Several posts on this forum suggest the following:


trace(MovieClip(this.parent).callRate);

…but this results in the following error:


TypeError: Error #1009: Cannot access a property or method of a null object reference.
       at S1/frame1()

Assistance much appreciated.