Adapt from this example:
<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default2.aspx.cs" Inherits="Default2" %>
<!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 id="Head1" runat="server">
<title></title>
<script type="text/javascript">
function validateNumberRange(sender) {
var e = sender;
var textboxVal = e.value;
if (textboxVal >= 0.00 && textboxVal <= 1.00) {
return true;
}
else
alert('Please enter a number between 0.00 to 1.00');
return false;
}
</script>
</head>
<body>
<form id="form1" runat="server">
<asp:GridView ID="GridView1" runat="server">
<Columns>
<asp:TemplateField HeaderText="Text Box Column">
<ItemTemplate>
<asp:TextBox ID="textbox1" runat="server" onkeyup="return validateNumberRange(this);"/>
</ItemTemplate>
</asp:TemplateField>
</Columns>
</asp:GridView>
</form>
</body>
</html>