Filter Activity lookup MSCRM Javascript

Hi All,

Please find the below JS code to filter Lookup Types

In my below Code am filtering requiredattendees, Call the below script in onload function

var lookuptypeIcons = "/_imgs/ico_16_2.gif:/_imgs/ico_16_8.gif";
var lookuptypenames = "contact:2:Contact,systemuser:8:User";
var lookuptypes = "2,8";

if (Xrm.Page.getAttribute("requiredattendees") != null) {
                $("#requiredattendees").focus(function () {
                    var toLookUp = $("img[attrName='requiredattendees']");
                    lookuptypes = "2,8";
                    if (toLookUp.length > 0) {
                        toLookUp[0].setAttribute("lookuptypenames", lookuptypenames);
                        toLookUp[0].setAttribute("lookuptypes", lookuptypes);
                        toLookUp[0].setAttribute("lookuptypeIcons", lookuptypeIcons);
                        toLookUp[0].setAttribute("createpermissiondictionary", "contact:true,systemuser:true");
                        toLookUp[0].setAttribute("DefaultViewId", "5DA08E4B-4493-E111-BEF2-00155DC87C59");
                        toLookUp[0].setAttribute("defaulttype", 2);
                    }
                });

            }