Style Tag in Wordpress Content Wysiwyg

Hi !

I would like to allow the users of my Wordpress site to use the <style> tag directly inside the default Wordpress wysiwyg (the_content). Right now, if he writes <style>...</style> than save, they are not saved. The styles disappears from the wysiwyg...

Could you please help me ?
I've seen this but I don't want to edit Wordpress core files... http://jack.ukleja.com/allow-style-elements-tags-within-wordpress-blog-for-inline-css/

Thanks !