Open custom page when user clicks on "Add New Item" in document library

<script src="/sites/SPortal/_layouts/SPortal_CustomScripts/jQuery/jquery-ui-1.8.16.custom/js/jquery-1.6.2.min.js" type="text/javascript"></script>

<script type="text/javascript">

$(document).ready(function(){

$("#idHomePageNewDocument").attr("onclick","javascript:NewItem2(event, \"http://abc-

004:12863/sites/SPortal/_layouts/SPortal/PW.CustomUpload.aspx?IsDlg=1\");javascript:return false;");

});</script>

<style type="text/css">

.UploadMultiple-Menu32.Upload.Menu.AddDocument.New.Documents#Ribbon {

        DISPLAY: none

}</style>