Dynamic Filter reporting hierarchy script

I'm trying to create a dynamic filter that will return the entire reporting hierarchy of the current user by looking at the manager field on sys_user.   So far, I've gotten it to pull the direct reports of the current user but I've not been able to get the direct report's of the current user's direct reports.   I would like to go six levels deep using something like this:

Current User -> Current User's Direct Reports -> Current User's Direct Report's Direct Reports

I thnk I need to use a while loop but I'm not quite sure how to do that.   Any thoughts?   Thanks!

Here's the script I have so far:

var getWithinMyReportingHierarchy = Class.create();

getWithinMyReportingHierarchy.prototype = {

      initialize: function() {

      },

getWithinMyReportingHierarchy:function(){

  var u = gs.getUserID();

  var gp = [];

  var g = new GlideRecord("sys_user");

  g.addQuery("manager", u);

  g.query();

  while( g.next()) {

  gp.push(g.sys_id.toString());

  }

  return gp;

  //

},

      type: 'getWithinMyReportingHierarchy'

};