custom button is not reloaded after CKEDITOR is rebuild

Hi!
I've another problem...

I've put CKEDITOR in a central frame...
and into my specific template I do this

 var editorCK = CKEDITOR.replace(  'm_sText', ... )

and then I add a button like in the sdk example

editorCK.on( 'pluginsLoaded', function( ev ) {
                       if ( !CKEDITOR.dialog.exists( 'internalLinkPanel' ) ) {
                            CKEDITOR.dialog.add( 'internalLinkPanel', '../internalLinkPanel.js' );
                        }
                        editorCK.addCommand( 'internalLinkPanelCmd', new CKEDITOR.dialogCommand( 'internalLinkPanel' ) );

                        editorCK.ui.addButton( 'internalLinkButton',
                        {
                            label : 'Collegamenti interni',
                            command : 'internalLinkPanelCmd'
                        });
                    });

and taht works fine...
but sometimes I reload the CKEDITO frame, and I got an error (The instance already exists )

the first solution was add something like this

                    if (CKEDITOR.instances["sText'"] != undefined) {                              
                        CKEDITOR.remove(CKEDITOR.instances[sText']);                            
                    } 

and it works fine.... the only problem is that my custom button is not recreated into my ckeditor istance...

can you help me???
thanks!!!!!!!!