Add external css stylesheet in drupal 6

<!--php
$inc_path = drupal_get_path('theme', 'your_theme_name') . '/path/name.css';
$file = realpath(".") ."/". $inc_path;
if(file_exists($file)) {
drupal_add_css($inc_path , 'theme', 'all', FALSE);
$vars['css']['all']['theme'][$inc_path] = 1; // this is what makes it work!
$vars['styles'] = drupal_get_css();
}
?-->