I am getting this case:
Inside a Wordpress blog I've my primary navigation persisting of groups. The navigation has been produced with wp_list_categories().

Now Let me mingle only one connect to a webpage in a certain position in this particular navigation built of just groups.

Any ideas the way i could make this happen?

Thanks!
sprain

Use http://codex.wordpress.org/Function_Reference/wp_list_pages and exclude the web pages you wouldn't want within the menu:

<php wp_list_pages(title_li&exclude=X;);?>

where 'X' may be the id quantity of the page you need to exclude. Or make use of a wordpress plugin like Exclude Pages.

Perform the same goes with http://codex.wordpress.org/Template_Tags/wp_list_categories to separate the course entries and set the page entries inside the category menu.

Use Reveal IDs for WP Admin « WordPress Plugins to locate page IDs.