I want change the color of the panel if i click checkbox using javascript

[itsenthil]

This is my UserControl(asc x) coding, it is not working plz help me to rectify the error.....what is wrong in that one.....

<%@ Control Language="vb" AutoEventWireup ="false" Codebehind="Use a.ascx.vb" Inherits="HIS.U sea" TargetSchema="h ttp://schemas.microso ft.com/intellisense/ie5" %>
<script language="javas cript" type="text/javascript">
function output()
{
var xx = document.getEle mentsByName("cb test").value;
// var xx=document.for ms.item('cbtest ');
//document.m
//var xx= document.forms. cbtest.checked= true;
// var mainForm=docume nt.mainForm.cbt est;
if (xx.checked ==true)
{
document.getEle mentById("Panel 1").style.backg roundColor= "#ffff00";
return true;
}
if(xx.checked == false)
{
document.getEle mentById("Panel 1").style.backg roundColor= "#90dd90";
return false;
}
}
</script>
<asp:panel id="Panel1" BackColor="Yell owGreen" runat="server" Width="56px" Height="40px" BorderStyle="No ne"
ToolTip="seat">
<asp:Image id="Image1" runat="server" Width="32px" Height="32px" ImageAlign="Mid dle" ImageUrl="file:///\\system107\HIS \Images\seat2.j pg"></asp:Image>
<INPUT id="cbtest" onclick="output ()" type="checkbox" name="cbtest" runat="server">
<asp:Label id="Label1" runat="server" Width="32px" Font-Size="X-Small" Font-Names="Verdana" ></asp:Label>
</asp:panel>

[kenobewan]

What error are you getting?

[itsenthil]

What error are you getting?

'Checked' is null or not an object