Dynamic text box

I am trying to change the text size of a dynamic text box’s text when a button is released. I am using flash 8.

The problem is the button to change the text size is in a different movieClip than the dynamic text box.

I thought that by using an absolute path to the dynamic text box I could get it to work but no luck.

Here is the code I am using on my button:

on (release) {
var myFormat = new TextFormat ();
myFormat.size = 20;
_root.a.b.c.setTextFormat = (myFormat);
}

a is the instance name of a movieClip on the main timeline

b is the instance name of a movieClip on the a movieClip timeline

c is the instance name of the dynamic text box on the b movieClip timeline

the button is on the a movieClip timeline

Please help…Please Please Please