updated value of asp.net label not reflected on java script variable

I have an asp.net label , label2 which is in an ajax update panel.

<div id="Div1" class="InsertBar">
   <asp:Label ID="Label2" 
            runat="server" Visible="true" Font-Bold="true">
   </asp:Label>    
      <asp:GridView>
        <!-- my gridview template and columns -->
      </asp:GridView>
   </asp:Panel>
</div>

This update panel is displayed in a jquery dialog. The jquery dialog is opened on button click event.

I am assigning a value for the label label2 in asp.net code behind on each button click.

I am trying to access label2 in the javascript code using the following code.

 var newtitle = $('#<%=Label2.ClientID%>').text();

The javascript function is below . The function is called from asp.net code behind

 <script type="text/javascript">
 function ViewModelPopup1() {

            var newtitle = $('#<%=label2.ClientID%>').text();

            $(Div1).dialog('option', 'title', newtitle);

        }
   </script>

The problem I have is , for the first time the asp.net button is clicked the javascript variable new title gets assigned to the asp.net label2. But on subsequent button clicks the javascript variable newtitle does not get updated . Any suggestions on how I can update the javascript variable to the asp.net label on each button click ?

Just my thoughts. I have the asp.net label within an ajax update panel. Should I also use any ajax for the javascript ???