Export Grid Async and Conditional Formatting

[Main Export Method ...]
BtnExportExcel.Enabled = false;
try
{
    GridViewSpreadExport spreadExporter = new GridViewSpreadExport(this.radGridView1);
    spreadExporter.ExportChildRowsGrouped = true;
    spreadExporter.HiddenColumnOption = Telerik.WinControls.UI.Export.HiddenOption.DoNotExport;
    spreadExporter.HiddenRowOption = Telerik.WinControls.UI.Export.HiddenOption.DoNotExport;
    spreadExporter.FileExportMode = FileExportMode.CreateOrOverrideFile;
    SpreadExportRenderer exportRenderer = new SpreadExportRenderer();
    spreadExporter.ExportVisualSettings = true;
    lastFileName = fileName;
    using (var bgw = new BackgroundWorker())
    {
        pgb_Saving.Value = 0;
        pnlSaving.Visible = true;
        var bgwFileName = fileName;
        bgw.DoWork += (o,e)=> spreadExporter.RunExport(bgwFileName, exportRenderer);
        bgw.RunWorkerCompleted += SpreadExporter_AsyncExportCompleted;
        bgw.RunWorkerAsync();
    }
                        
}
catch (Exception ex)
{
    BtnExportExcel.Enabled = true;
}
[...]

private void SpreadExporter_AsyncExportCompleted(object sender, AsyncCompletedEventArgs e)
{
    pgb_Saving.Value = 0;
    pnlSaving.Visible = false;
    tsbDataGridViewExportExcel.Enabled = true;
    if (e.Error is null && System.IO.File.Exists(lastFileName))
    {

        string szTemp = "'" + lastFileName + "' created.\r\n\r\nWould you like to open the spreadsheet?";
        var iRet = MsgBox.ConfirmMsg(szTemp, MessageBoxButtons.YesNo, "Spreadsheet Created");
        if (iRet == DialogResult.Yes) System.Diagnostics.Process.Start(lastFileName);
    }
    SwapForExport(false);
}

private void pnlSaving_VisibleChanged(object sender, EventArgs e)
{
    if (pnlSaving.Visible)
    {
        if (pnlSaving.Tag  as Timer is null) {
            var tmr = new Timer() { Interval = 250 };
            tmr.Tick += Timer_Tick;
            pnlSaving.Tag = tmr;
                }
        ((Timer)pnlSaving.Tag).Start();
    }
    else
    {
        if(pnlSaving.Tag is Timer tmr)
        {
            tmr.Stop();
        }
    }
}

private void Timer_Tick(object sender, EventArgs e)
{
//pgb_Saving is a Progress Bar
    pgb_Saving.Value = (pgb_Saving.Value + 1) % pgb_Saving.Maximum;
}