Thank you, Viktor, for the answer.
But I be doing wrong. I created a field of type Select Dynamic to fetch in #__categories based on parent_id and the set as a multiple.
When I did what you recommended did not return any results and still got the error: htmlspecialchars () expects parameter 1 to be string, array Given in /var/www/develop3/libraries/cms/cck/plugin/field.php on line 827.
Any suggestions?
Regards,