Problem exporting filtered rows only to Excel from RadGridView...

I have a standard RadGridView that I've created functionality to export to Excel.  When I filter the rows of the RadGridView and then execute my export button, the spreadsheet still contains all of the rows.  How can I export filtered rows only ?

I've already tried ExcelML and that doesn't seem to export to .XLSX  format.  It does handle the filtering automatically.

 

Here is my code:

 

private void radButton_Export_Click_1(object sender, EventArgs e)
        {
            Cursor = Cursors.WaitCursor;
            GridViewSpreadExport spreadExporter = new GridViewSpreadExport(this.radGridView1);
            SpreadExportRenderer exportRenderer = new SpreadExportRenderer();
            RadOpenFolderDialog FolderDL = new RadOpenFolderDialog();
            
            FolderDL.InitialDirectory = @"\\mansply.local\shares\sales$\";
            FolderDL.ExpandToCurrentDirectory = false;
            DialogResult FolderDLR = FolderDL.ShowDialog();
            if (FolderDLR == DialogResult.OK)
            {
                string foldername = FolderDL.FileName;

                spreadExporter.RunExport(foldername + @"\ExportTest" + "-" + DateTime.Now.ToString("yyyyMMddhhmmss") + ".xlsx", exportRenderer);      
            }
            Cursor = Cursors.Default;
        }