MySQL - insert rows into table where no matches found in column?

Hi,
I want to insert new rows into my table, but only if the icon_name does not already exist.
What is the best way to do this?

Thanks in advance for your help.

INSERT INTO `icons` (`icon_name`) VALUES ('page one');
INSERT INTO `icons` (`icon_name`) VALUES ('help page');
INSERT INTO `icons` (`icon_name`) VALUES ('another page');



CREATE TABLE IF NOT EXISTS `icons` (
  `id` tinyint(3) NOT NULL auto_increment,
  `icon_position` tinyint(3) default '100',
  `icon_name` varchar(120) NOT NULL,
  `visible` enum('1','0') default '1',
  PRIMARY KEY  (`id`)
) ENGINE=MyISAM  DEFAULT CHARSET=latin1 AUTO_INCREMENT=12 ;

--
-- Dumping data for table `icons`
--

INSERT INTO `icons` (`id`, `icon_position`, `icon_name`, `visible`) VALUES
(1, 0, 'was one', '1'),
(2, 4, 'help page', '1'),
(3, 1, 'was three', '0'),
(11, 100, 'new_webpage', '1');