<asp:TextBox ID="NodeText" runat="server"></asp:TextBox>
   <script src="JS/jquery-1.4.2.js" type="text/javascript"></script>
    <script type="text/javascript">
        $(function() {
  $("input#NodeText").bind({ contextmenu: function(e) {
                if (e.which == 3)
                    return false;
            },
                keyup: function() {
                    $(this).val("");
                }
            });
   });
    </script>