Customer Validator

  <asp:CustomValidator ID="CustomValidator1" runat="server" ErrorMessage="CustomField must be an even number!"
ControlToValidate="CustomField" ClientValidationFunction="ValidateEvent"
OnServerValidate="ValidateEvent">
  </asp:CustomValidator>


  <script type="text/javascript">

   function ValidateEvent(oSrc, args)
     {

args.IsValid = ((args.Value % 2) == 0);
      }

  </script>


   protected void ValidateEvent(object source, ServerValidateEventArgs args)
  {

    if ((Convert.ToInt32(args.Value) % 2) == 0)
            args.IsValid = true;
    else
            args.IsValid = false;


  }