ActionScript 2.0 Language Reference - Adobe Help and Support

Parameters
methodName:String - The name by which the ActionScript function can be called from
JavaScript. This name does not need to match the actual name of the ActionScript method.
instance:Object - The object to which this resolves in the method. This object is not
necessarily the object on which the method can be found — you can specify any object (or
null).
method:Function - The ActionScript method to be called from JavaScript.
Returns
Boolean - If the call succeeded, returns true. If it failed because the instance was not
available, a security restriction was encountered, there was no such function object, a
recursion occurred, or something similar, returns false.
A return value of false may also mean that the containing environment belongs to a security
sandbox to which the calling code does not have access. You can work around this problem by
doing the following:
■ In the tag for the SWF file in the containing HTML page, set the following
parameter:
■ In the SWF file, add the following ActionScript:
System.security.allowDomain(sourceDomain)
Example
The following example registers the goToAdobe() function as callable from the container
with the name goHome.
import flash.external.*;
var methodName:String = "goHome";
var instance:Object = null;
var method:Function = goToAdobe;
var wasSuccessful:Boolean = ExternalInterface.addCallback(methodName,
instance, method);
var txtField:TextField = this.createTextField("txtField",
this.getNextHighestDepth(), 0, 0, 200, 50);
txtField.border = true;
txtField.text = wasSuccessful.toString();
ExternalInterface (flash.external.ExternalInterface) 559