Display the content of a CCK Field in the html meta tags ???

Hi !
I've juste installed the CCK module, in the documentation i read we could precisely position where a given CCK field is displayed by modifying hte node-thenodetype.tpl.php files ( for example by writing "print content_format('field_first_name', $field_first_name[0]);" )

but what if i want to display that content in the html meta tags ?? ( for example i plan to create a description and a keywords field ), as the node.tpl.php only controls the content itself and not the surrounding html code ....

thanks