how to close SharePoint modal from xls

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SharePoint2010

I have a link that generates a SharePoint Modal Dialog which results in an EXCEL spreadsheet. It works fine except when I close the EXCEL document, the document unloads but the parent page stays in Modal Mode. Is there any way to solve this? Below is the Java Script from the parent page.

function OpenAdvertisedDialog() {
          var dialogOptions = {
              url: "/_layouts/apply/reports/advertised_billets.aspx",
              autoSize: true,
              allowMaximize: false,
              dialogReturnValueCallback: onCloseCallback
          };
          SP.UI.ModalDialog.showModalDialog(dialogOptions)
      }


      function onCloseCallback(dialogResult, returnValue) {
          SP.UI.ModalDialog.RefreshPage(SP.UI.DialogResult.OK);
      }

Here is code behind creating XLS

  private void ExportToExcel()
        {
            //Export the GridView to Excel

            PrepareGridViewForExport(gvReport);
            string style = @"<style> .text { mso-number-format:\@; } </style> ";

            string attachment = "attachment; filename=Advertised Billets Report.xls";

            Response.ClearContent();

            Response.AddHeader("content-disposition", attachment);

            Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";

            StringWriter sw = new StringWriter();

            HtmlTextWriter htw = new HtmlTextWriter(sw);

            gvReport.RenderControl(htw);

            Response.Write(style);
            Response.Write(sw.ToString());

            Response.End();
        }