Getting a current HTTP address

I’m sure this a common Actionscript method, but my websearch on how to do this is turning up no results.

Using MX 2004 I am trying to get the current value of the web address in which the swf is residing and have actions take place based on the HTTP locations.

var a:String = this.HTTPaddress;
var b:String = this.HTTPaddress;

(have certain actions take place based on above vars.)

Thanks for all your help!