Uploadify and Modalpopupextender

Hi

I am trying to use the Uploadify control from within a modalpopupextender, however I cannot get the javascript to recognise the input control.

How do I reference the inout control (or any other control for that matter) from within a modalpopupextender?

<script type="text/javascript">
            $(function () {
                $("#<%=file_upload_reply.ClientID%>").uploadify({
                    'swf': '../Uploadify/uploadify.swf',
                    'uploader': '../Uploadify/VBHandlerReply.ashx?accountid=<%=AccountId%>&ticketguid=<%=TicketReplyGuidId%>&ticketid=<%=TicketId%>',
                    'cancelImg': '../Uploadify/uploadify-cancel.png',
                    'buttonText': 'Select Files',
                    'multi': true,
                    'auto': true,
                    'removeCompleted': false,
                    'fileSizeLimit': '4MB'
                });
            })</script>

and the input control is as follows:

<inputtype="file"name="file_upload_reply"id="file_upload_reply"runat=server/>