Thanks!
========== Parent Page ======================
<%@ Page Language="C#" %>
<%@ Register Assembly="Telerik.Web.UI" Namespace="Telerik.Web.UI" TagPrefix="telerik" %>
<html><body><form id="form1" runat="server">
<telerik:RadScriptManager ID="RadScriptManager1" runat="server"></telerik:RadScriptManager>
<telerik:RadWindow ID="RadWindow1" runat="server" NavigateUrl="TestPrintMenu_SubPage.aspx" VisibleOnPageLoad=true></telerik:RadWindow>
</form></body></html>
=========== Sub Page with Menu ================
<%@ Page Language="C#" %>
<%@ Register Assembly="Telerik.Web.UI" Namespace="Telerik.Web.UI" TagPrefix="telerik" %>
<html>
<script type="text/javascript">
function printWindow(){
var menu = $find("mainMenu");
menu.close();
window.print();}
</script>
<body><form id="form1" runat="server">
<telerik:RadScriptManager ID="RadScriptManager1" runat="server"></telerik:RadScriptManager>
<telerik:RadMenu ID="mainMenu" runat="server" Skin="Vista" ClickToOpen="True">
<CollapseAnimation Type="OutQuint" Duration="200"></CollapseAnimation>
<Items>
<telerik:RadMenuItem runat="server" Text="File">
<Items>
<telerik:RadMenuItem runat="server" NavigateUrl="javascript: printWindow();" Text="Print"></telerik:RadMenuItem>
<telerik:RadMenuItem runat="server" IsSeparator="True" Text="-"></telerik:RadMenuItem>
<telerik:RadMenuItem runat="server" Text="Close"></telerik:RadMenuItem>
</Items>
</telerik:RadMenuItem>
</Items>
</telerik:RadMenu>
</form></body></html>