Okay, i found something:
<script type="text/javascript"<
var oFCKeditor = new FCKeditor( 'MyTextarea' ) ;
oFCKeditor.BasePath = '/drupal/sites/all/modules/FCKEditor/fckeditor/';
oFCKeditor.Config['CustomConfigurationsPath'] = "/drupal/sites/all/modules/FCKEditor/fckeditor.config.js";
oFCKeditor.ReplaceTextarea() ;
</script>
i put it after the textarea html code, but it tells me alway that the “FCKEditor is not defined”… ??