EDIT

    var token = new Date().getTime()/1000|0;//'1234'; //use the current timestamp as the token value

    jQuery('#downloadTokenValueId').val(token);

      fileDownloadCheckTimer = window.setInterval(function () {

          var cookieValue = jQuery.cookie('fileDownloadToken');

          if (cookieValue == token) {

              finishDownload();

          }

      }, 1000);

      jQuery.blockUI( { message:'</br><h1><img src="../css/jquery-ui/images/ajax-loader.png">Please wait until the file is ready to download...</h1><br/>'});

  }