open other dialog in api

                                        onClick: function () {

                                            for (var i in CKEDITOR.instances) {
                                                var currentInstance = i;
                                                break;
                                            }
                                            var oEditor = CKEDITOR.instances[currentInstance];
                                            var pluginName = 'specialchar',
                                                plugin = this;

                                            // Register the dialog.
                                            CKEDITOR.dialog.add(pluginName, this.path + 'dialogs/specialchar.js');

                                            editor.addCommand(pluginName, {
                                                exec: function () {
                                                    var langCode = editor.langCode;
                                                    langCode =
                                                        plugin.availableLangs[langCode] ? langCode :
                                                        plugin.availableLangs[langCode.replace(/-.*/, '')] ? langCode.replace(/-.*/, '') :
                                                        'en';

                                                    CKEDITOR.scriptLoader.load(CKEDITOR.getUrl(plugin.path + 'dialogs/lang/' + langCode + '.js'), function () {
                                                        CKEDITOR.tools.extend(editor.lang.specialchar, plugin.langEntries[langCode]);
                                                        editor.openDialog(pluginName);
                                                    });
                                                },
                                                modes: { wysiwyg: 1 },
                                                canUndo: false
                                            });

why do not open dialog?