private function manageEditDocumentEnterProperties(&$params, &$dmsLoader, &$manageCategory, &$arrMessages, &$blnShowStart, $documentId)
  {
    $params->loadRootCategory = true; // get complete path to root, for checking inherited access rights
    $params->loadAccessRights = true;
    $params->loadDocuments = false;
    $category = $dmsLoader->loadCategory($manageCategory, $params);
    
    if (!$category->isEditableForCurrentMember())
    {
      $arrMessages['errors'][] = $GLOBALS['TL_LANG']['DMS']['ERR']['manage_document_not_allowed'];
      $blnShowStart = true;
    }
    else
    {
      $document = $dmsLoader->loadDocument($documentId, $params);
      
      // load existing documents for file name
      $params->loadCategory = true; // need the category of existing documents
      $existingDocuments = $dmsLoader->loadDocuments($document->fileName, $document->fileType, $params);
      $params->loadCategory = false;
      
      $existingDocuments = array();
      $blnCategoriesDiffer = false; // check if an existing document is in another category
      foreach ($existingDocuments as $existingDocument)
      {
        if ($existingDocument->id != $documentId)
        {
          $existingDocuments[] = $existingDocument;
          // will be true, if one is true (keep true status, if once set)
          $blnCategoriesDiffer = $blnCategoriesDiffer || ($category->id != $existingDocument->categoryId);
        }
      }
      if ($blnCategoriesDiffer)
      {
        $arrMessages['warnings'][] = $GLOBALS['TL_LANG']['DMS']['WARN']['edit_existing_document_in_another_catagory'];
      }
      
      $this->Template = new \FrontendTemplate("mod_dms_mgmt_manage_document_edit");
      $this->Template->setData($this->arrData);
      
      $this->Template->category = $category;
      $this->Template->document = $document;
      $this->Template->existingDocuments = $existingDocuments;
      
      if (!$category->isPublishableForCurrentMember())
      {
        $arrMessages['infos'][] = $GLOBALS['TL_LANG']['DMS']['INFO']['publish_document_not_allowed'];
      }
      
      $blnShowStart = false;
    }
  }