I have done many projects in ActionScript 2, but now I am creating a website in ActionScript 3.0. I’ll give you a walkthrough of what I have.

Scene: contains a brief animation, a stop action at the end, and a MovieClip that I’ll call Menu.

Menu: contains a script layer and two MovieClips, one I’ll call Pages and the other, Navigation.
On the script layer we have MouseEvent.CLICK and MouseEvent.ROLL_OVER for each button inside of Navigation.
The MouseEvent.CLICK animates labels in Pages.
The MouseEvent.ROLL_OVER animates labels in Navigation.
Also, there is a stop action.

Pages: contains each page appearance, labels to point to each, and stop actions to keep them separate.

Navigation: contains the buttons (btn1, btn2, btn3, and btn4), each ROLL_OVER animation, labels to point to each, and stop actions to keep them separate.

The problem that I’m having is that I get undefined property errors for the buttons. Each button is named appropriately and instanced appropriately as far as I can tell.

CLICK script:
function mainBtn1Down(event:MouseEvent):void {
pages.gotoAndPlay("page1");
}
function mainBtn2Down(event:MouseEvent):void {
pages.gotoAndPlay("page2");
}
function mainBtn3Down(event:MouseEvent):void {
pages.gotoAndPlay("page3");
}
function mainBtn4Down(event:MouseEvent):void {
pages.gotoAndPlay("page4");
}
btn1.addEventListener(MouseEvent.CLICK, mainBtn1Down);
btn2.addEventListener(MouseEvent.CLICK, mainBtn2Down);
btn3.addEventListener(MouseEvent.CLICK, mainBtn3Down);
btn4.addEventListener(MouseEvent.CLICK, mainBtn4Down);

ROLL_OVER script:
function main1Over(event:MouseEvent):void {
gotoAndPlay("down1");
}
function main2Over(event:MouseEvent):void {
gotoAndPlay("down2");
}
function main3Over(event:MouseEvent):void {
gotoAndPlay("down3");
}
function main4Over(event:MouseEvent):void {
gotoAndPlay("down4");
}
btn1.addEventListener(MouseEvent.ROLL_OVER, main1Over);
btn2.addEventListener(MouseEvent.ROLL_OVER, main2Over);
btn3.addEventListener(MouseEvent.ROLL_OVER, main3Over);
btn4.addEventListener(MouseEvent.ROLL_OVER, main4Over);