Hi
Try this code.
Written in JQuery..
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="test.aspx.cs" Inherits="POC.test" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<script src="jquery-1.10.2.js" type="text/javascript"></script>
<title></title>
<script type="text/javascript">
function Sum(thisctrol) {
var $row = $(thisctrol).parent().parent();
var Rebate = $("[id*='txtRebate']", $row).val();
var Sales = $("[id*='txtSales']", $row).val();
if (Rebate == '' || Sales == '') {
alert('txtRebate and txtSales should not be empty');
$("[id*='lblRebate']", $row).html('');
}
else {
var x = parseFloat(Rebate);
var y = parseFloat(Sales);
$("[id*='lblRebate']", $row).html((x * y) / 100);
}
}
</script>
</head>
<body>
<form id="form1" runat="server">
<asp:GridView ID="gv" runat="server">
<Columns>
<asp:TemplateField>
<ItemTemplate>
<asp:TextBox ID="txtRebate" onchange="Sum(this)" runat="server"></asp:TextBox>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField>
<ItemTemplate>
<asp:TextBox ID="txtSales" onchange="Sum(this)" runat="server"></asp:TextBox>
</ItemTemplate>
</asp:TemplateField>
<asp:TemplateField>
<ItemTemplate>
<asp:Label ID="lblRebate" runat="server" Text="..."></asp:Label>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
</form>
</body>
</html>