code: function addOption( combo, optionText, optionValue, documentObject, index )
  	{
  		combo = getSelect( combo );
  		var oOption;
  		if ( documentObject )
  			oOption = documentObject.createElement( "OPTION" );
  		else
  			oOption = document.createElement( "OPTION" );
  
  		if ( combo && oOption && oOption.getName() == 'option' )
  		{
  			if ( CKEDITOR.env.ie ) {
  				if ( !isNaN( parseInt( index, 10) ) )
  					combo.$.options.add( oOption.$, index );
  				else
  					combo.$.options.add( oOption.$ );
  
  				oOption.$.innerHTML = optionText.length > 0 ? optionText : '';
  				oOption.$.value     = optionValue;
  			}
  			else
  			{
  				if ( index !== null && index < combo.getChildCount() )
  					combo.getChild( index < 0 ? 0 : index ).insertBeforeMe( oOption );
  				else
  					combo.append( oOption );
  
  				oOption.setText( optionText.length > 0 ? optionText : '' );
  				oOption.setValue( optionValue );
  			}
  		}
  		else
  			return false;
  
  		return oOption;
  	}
docs: Add a new option to a SELECT object (combo or list).