Loading a Menu MovieClip

[rn2071]

Greetings,

I'm new to AS3, so I'm giving myself a pretty big project to learn it. I've been able to figure most things out with the help of Tutorials and useful AS3 tips up until now.

Basically, I've create a movieClip called mcGui that uses the class Gui. Within the movieClip I've created frame labels and places buttons and text at the different frames. There's a label named "title" which resides on the first frame and has the button btnStart. There's a label named "story" that resides on the tenth frame and has the button btnNext.

Now, I call this movieClip from my main timeline with:

var myGui:Gui = new Gui("story");
addChild(myGui);

Here's the Gui.as class:

package com {

import flash.display.MovieClip;
import flash.display.SimpleButton;
import flash.events.*;

public class Gui extends MovieClip {

function Gui(lbl:String) {
this.gotoAndStop(lbl);
trace(this.currentFrame);

switch (lbl) {
case "title":
btnStart.addEventListener(MouseEvent.CLICK, fncStart);

break;

case "story":
btnNext.addEventListener(MouseEvent.CLICK, fncNext);
break;
}
}

function fncStart(e:MouseEvent):void {
trace("START");
}

function fncNext(e:MouseEvent):void {
trace("NEXT");
}

}
}

Now, my trace function shows that I am going to frame 10 on my movieClip, however I keep getting this error.

TypeError: Error #1009: Cannot access a property or method of a null object reference.
at com::Gui()
at test_r1_fla::MainTimeline/frame1()

It don't get this error if I try to go to the "title" frame label. So, it's like the btnNext doesn't exist.

Any ideas? I'm really stuck on this.