getting error calculting the total of gridview cells using javascript

Question

Hi all,

I am calculating the total of one gridivew cells using javascript and displaying the resul in gridivew

footer. but i am getting this exception

Microsoft JScript runtime error: 'document.getElementById(...)' is null or not an object

Here is my code:

<asp:GridView ID="gv" runat="server" AutoGenerateColumns="false" ShowFooter="true"> 

   <Columns>      

       <asp:TemplateField>

          <ItemTemplate>

             <asp:TextBox ID="TextBox1" runat="server" onkeyup="Calculate('gv')" />

         </ItemTemplate>

         <FooterTemplate>

            <asp:TextBox ID="total" runat="server" Text="0" Width="83px"></asp:TextBox>

         </FooterTemplate>

   </Columns>

</asp:GridView>

 <script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jquery/jquery-1.5.js"></script>  

    <script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jquery.ui/1.8.10/jquery-ui.js"></script>    

    <script type="text/javascript">

function Calculate(GridView)

{

   var total = 0;   

   var gridview = document.getElementById('<%=Gridview1.ClientID %>').getElementsByTagName("input");

    

   for ( i = 0; i < gridview.rows.length; i ++)

   {

       var node = gridview.rows[i].cells[2].childNodes[2]; //textbox  

       if (node != undefined && node.type == "text") //check only textbox, ignore empty one

            if (!isNaN(node.value) && node.value != "") //check for valid number

               total += parseInt(node.value); 

   }

   document.getElementById("total").innerHTML = total.toString(); //display

}