[AS3] Changing stage variables from within a movie clip

I'm brand new at as3, just switched from as2. I want to change variables on the main stage's code from within a movie clip.

Say for example, I want to change a variable called 'chair'

In AS2, this is how I would do it:

(on the main stage)

Code:

---

chair = 2;

---

(in the movie clip)

Code:

---

_root.chair = 1;

---

So in AS3 I have:
(stage)

Code:

---

var chair:Number = 2;

---

(movie clip)

Code:

---

_root.chair = 1;

---

But all I get is a 1119 error saying 'Access of possibly undefined property chair through a reference with static type flash.display:DisplayObject.'

I tried googling this problem but I couldn't quite word it right. Help?

Actionscript Code:

MovieClip(root).chair=1

:D Thank you very much

I do have one more minor question

My movie clip is set to stop at frame 1. I set a var to trigger my movie clip to gotoAndPlay (2);

It just goes to 2 and stops. I tried adding play(); to frame 2 in the movie clip but it still gets stuck on frame 2. :/

Could you post the code or possibly even the FLA file?