PopUp is not showing after Excel Download?

I'm writing data into an excel and after completion I'm downloading the excel sheet.

This is my code for downloading

byte[] fileBytes = System.IO.File.ReadAllBytes(excelPath);
        System.Web.HttpContext context = System.Web.HttpContext.Current;
        context.Response.Clear();
        context.Response.ClearHeaders();
        context.Response.ClearContent();
        context.Response.AppendHeader("content-length", fileBytes.Length.ToString());
        context.Response.ContentType = "application/octet-stream ";
        context.Response.AppendHeader("content-disposition", "attachment; filename=" + "ExcelSheet.xls");
        context.Response.BinaryWrite(fileBytes);
        context.ApplicationInstance.CompleteRequest();

After completion of this I'm calling my JavaScript for Popup

    ScriptManager.RegisterStartupScript(this, this.GetType(), "Pop", "openModal();", true);
    lblLog.Text = "Successfully Downloaded";

But it is not showing the popup. If I remove the code for download it is working perfectly.What should I do to downlod and get poup.