Hi,
This will indeed require custom code for now as this has not been implemented. I add this on our todo list.
The best would be to create a new mass action plugin:
And use as main function the function "onProcessOrderMassActionexportCsv", the current function for the default "export csv file" is :
	function onProcessOrderMassActionexportCsv(&$elements,&$action,$k){
		$formatExport = $action['formatExport']['format'];
		$email = $action['formatExport']['email'];
		$path = $action['formatExport']['path'];
		if(!empty($path)){
			$url = $this->massaction->setExportPaths($path);
		}else{
			$url = array('server'=>'','web'=>'');
			ob_get_clean();
		}
		$app = JFactory::getApplication();
		if($app->isAdmin() || (!$app->isAdmin() && !empty($path))){
			$params = new stdClass();
			$params->action['order']['order_id'] = 'order_id';
			unset($action['formatExport']);
			$params = $this->massaction->_displayResults('order',$elements,$action,$k);
			$params->formatExport = $formatExport;
			$params->path = $url['server'];
			$params = $this->massaction->sortResult($params->table,$params);
			$this->massaction->_exportCSV($params);
		}
		if(!empty($email) && !empty($path)){
			$config = hikashop_config();
			$mailClass = hikashop_get('class.mail');
			$content = array('type' => 'csv_export');
			$mail = $mailClass->get('massaction_notification',$content);
			$mail->subject = JText::_('MASS_CSV_EMAIL_SUBJECT');
			$mail->html = '1';
			$csv = new stdClass();
			$csv->name = basename($path);
			$csv->filename = $url['server'];
			$csv->url = $url['web'];
			$mail->attachments = array($csv);
			$mail->dst_name = '';
			$mail->dst_email = explode(',',$email);
			$mailClass->sendMail($mail);
		}
	}As you can see we are calling functions from the mass action class, so you can handle the data instead of the call:
$this->massaction->_exportCSV($params);