set html elemet

hi i use this code

   set default _divPreview

   var _divPreview = '<div style="text-align:center;"><div  id="lll">AaBbYyGgLlJj</div><br></div>';

  {id: 'htmlPreview',

  type: 'html',
  html: _divPreview}

i want to update _divPreview

   var _ckDialog = window.CKEDITOR.dialog.getCurrent();

   _ckDialog.getContentElement('tab-page1', 'htmlPreview').html('<div"><br /><div>شهاب</div><br>/div>');

but not chenge !(: