asp.net BackGroundWorker RunWorkerCompleted

I have an async process called from javascript using a PageMethod that executes a potentially long running process and updates a progress bar.  I'm trying to capture any errors/messages from the async process and report it to the user on a page control.  Tried sending a message from RunWorkerCompleted to the async success callback, but with no luck.

any help would be greatly appreciated.

Including relevant code.

thanks

// ** aspx code behind

Imports System.ComponentModel
Imports System.Threading
Imports System.Web.Services


    Protected Shared Sub ExportTaxesServices(ByVal sender As Object, ByVal e As DoWorkEventArgs)
        Dim dt As New DataTable

        ' Do the long running process
        Try
            args = CType(e.Argument, List(Of String))

            ' run the method to get rows for the datatable.   excluded for clarity
            For Each row As DataRow In dt.Rows

                    ' Calculate the percentage complete for this routine
                    percentComplete = Convert.ToInt32(i * 100 / rowCount)

                    ' Send the percentage complete to the async process that updates the rogress bar
                    bgWorker.ReportProgress(percentComplete)
                    i += 1
            Next
        Catch ex As Exception
            Throw ex
        End Try

    End Sub


    ' Return the percentage completed  
    <WebMethod()> _
    Public Shared Function Progress() As Integer
        Return percentage

    End Function

    ' Cancel the async call
    <WebMethod()> _
    Public Shared Sub CancelAsync()
        bgWorker.CancelAsync()

    End Sub

    ' Main routine that initiates the async call
    <WebMethod()> _
    Public Shared Sub RunAsync(ByVal taxType As String, ByVal invoiceDate As String, ByVal startDate As String, ByVal endDate As String, _
                               ByVal cycleID As String, ByVal userID As String)

        ' Add the list of parameters received from the javascript async call to a List
        Dim args As New List(Of String)
        args.Add(invoiceDate)
        args.Add(startDate)
        args.Add(endDate)
        args.Add(cycleID)
        args.Add(userID)

        percentage = 0

        ' Create the backgroundworker to execute the async calls on a separate thread
        bgWorker = New BackgroundWorker()
        bgWorker.WorkerReportsProgress = True
        bgWorker.WorkerSupportsCancellation = True

        Select Case taxType
            ' Set which routine will be run asynchronously
            Case "Services"
                AddHandler bgWorker.DoWork, AddressOf ExportTaxesServices

            Case "Usage"
                AddHandler bgWorker.DoWork, AddressOf ExportTaxesUsage

        End Select

        ' Set the routine that will be called when the progess of the async call changes
        AddHandler bgWorker.ProgressChanged, AddressOf bgWorker_ProgressChanged
        AddHandler bgWorker.RunWorkerCompleted, AddressOf bgWorker_Completed

        ' Start the async process, passing in the parameters
        Try
            bgWorker.RunWorkerAsync(args)
        Catch ex As Exception
            Throw ex
        End Try

    End Sub

    ' Gets the percentage completed of the async call
    Private Shared Sub bgWorker_ProgressChanged(ByVal sender As Object, ByVal e As ProgressChangedEventArgs)
        percentage = e.ProgressPercentage

    End Sub
    Private Shared Function bgWorker_Completed(ByVal sender As Object, ByVal e As RunWorkerCompletedEventArgs) As String
        Return "ok"

    End Function

// ** aspx javascript code

    <script type="text/javascript" language="javascript">

        var stopped = false;
        // Starts the async process with parameters if page passes validation
        if (Page_ClientValidate()) {
            function beginRequestHandler(sender, args) {
                stopped = false;
                var invoiceDate = new Date($get('<%= txtInvoiceDate.ClientID %>').value);
                invoiceDate = invoiceDate.getFullYear() + "-" + (invoiceDate.getMonth() + 1) + "-" + invoiceDate.getDate();

                var startDate = new Date($get('<%= txtStartDate.ClientID %>').value);
                startDate = startDate.getFullYear() + "-" + (startDate.getMonth() + 1) + "-" + startDate.getDate();

                var endDate = new Date($get('<%= txtEndDate.ClientID %>').value);
                endDate = endDate.getFullYear() + "-" + (endDate.getMonth() + 1) + "-" + endDate.getDate();

                var ddlCycleID = $get('<%= ddlBillingCycle.ClientID %>');
                var cycleID = ddlCycleID.options[ddlCycleID.selectedIndex].value;

                var ddlType = $get('<%= ddlType.ClientID %>');
                var taxType = ddlType.options[ddlType.selectedIndex].value;

                var userID = '<%= Session("UserID") %>';

                $get('<%= btnConfirm.ClientID %>').disabled = 'disabled';
                $get('<%= btnCancel.ClientID %>').disabled = 'disabled';
                $get('<%= progressPercent.ClientID %>').innerHTML = '0%';
                $get("<%= panelMessages.ClientID %>" + "_MessagePanel").style.display = 'none';
                $get('progressBar').style.width = '0%';
                PageMethods.RunAsync(taxType, invoiceDate, startDate, endDate, cycleID, userID, runAsyncSuccess, runAsyncFailure);
                setTimeout("progressChanged()", 10);
            }
        }

        // Closes the progress bar window and calls the function to refresh grid with results after the async call completes successfully.
        function runAsyncSuccess(result) {
            if (!stopped) {
                $find('modalProgressBehaviorID').hide();
                $get('<%= btnConfirm.ClientID %>').disabled = '';
                $get('<%= btnCancel.ClientID %>').disabled = '';
                $get('<%= btnCalculate.ClientID %>').disabled = 'disabled';
                refreshGrid('<%=hfRefereshGrid.ClientID %>');
                alert(result.get_message());
            }
            stopped = false;
        }

        function runAsyncFailure(result) {
            alert(result.get_message());
        }

        // Calls the Progress method to get the percent complete of the async process
        function progressChanged() {
            PageMethods.Progress(progressSuccess);
        }

        // Updates the progress bar with the percent complete of the async process
        function progressSuccess(response) {
            $get('<%= progressPercent.ClientID %>').innerHTML = response + '%';
            $get('progressBar').style.width = response + '%';
            setTimeout("progressChanged()", 10);
        }

        // Cancels the async process
        function cancelAsync() {
            stopped = true;
            PageMethods.CancelAsync();
        }

        // Refreshes the the grid with the results using an async postback
        function refreshGrid(hiddenFieldID) {
            var hiddenField = $get(hiddenFieldID);
            if (hiddenField) {
                hiddenField.value = (new Date()).getTime();
                __doPostBack(hiddenFieldID, '');
            }
        }
       
   </script>