Drupal 7 - Add CSS for specific paths

template.php

function THEMENAME_preprocess_page(&$vars) {

  // Add "addcourse.css" to Add Course page only  
  if(strstr($_SERVER['REQUEST_URI'], "admin/commerce/products/$path_alias")) {
    drupal_add_css(
      path_to_theme() . '/css/addcourse.css',
      array(
        'group' => CSS_THEME,
      )
    );
  };
  
}