Controling main movie from external swf

programming flash
1

Hi experts,
I have two files
main.swf and external.swf

i have use the following script on main.swf to do animation

import mx.transitions.Tween;
import mx.transitions.easing.*;

 
btn.onRelease = function(){
new Tween(_root.textBox,"_x",Strong.easeOut,_root.textBox._x, 100,1,true);//2 is the num of seconds
new Tween(_root.textBox,"_width",Strong.easeOut,_root.textBox._width,400,2,true)

which work perfectly fine.

Now due some reason i had to place the navigation bar in the external movie clip , in external.swf
Using the same script how can i control the textBox animation which is on the main.swf??
please help.