getURL() and POST


I am having trouble passing variables to my server. The following code is on a button:

on (release)
	var Username:String = user;
	var Password:String = pass;
	var RedirectTo:String = "/xnet/xnet_knowman.nsf/start?Open"

	getURL("/servlet/KX_loginProxy", "_parent", "GET");

“user” and “pass” are the var names of two input fields (text objects). The problem is that it is only passing “user” and “pass” variables. I need the script to pass Username, Password, and RedirectTo.

Any help will be appreciated. Thanks.