COURSEPRESS - main site, subsites : how promote subsites courses on main site ?


I would like to know if you could help me with this :

My WpMU is built like this :
- a main site with an automatic default "template" for subsites that are created after. So main site is a "home"/"landing" (where I would like present courses that have been created in an other subsite).
- subistes, one for each teacher, each teacher has his proper courses.

So, I would like use Shortcodes in order to feature somes subsites courses on the main site.

If I try, for example in an article on the mainsite, I write a shortcode with course_id=51, it seems search id 51 on mainsite. But in fact, it's id51 of a subsite precisely.
So it's doesn't work like this, all likes built like this are broken.

In order words, i need to use shortcode on mainsite, to point on subsites courses.

Thanks you in advance and have a good day !

Best regards