Am i missing something?

class test extends MovieClip {
private var butnPath;

function test() {
butnPath = this.cool_button
I assign this custom class to a MC containing a button with a instance name ‘cool_button’.
This code gives a me a compile error of ‘variable cool_button not defined’, what i am trying to do is reference something that is in the MC itself. The only solution i have found is to name the var the same as the instance name you are trying to reference.