Move multisite + BP from root to sub-dir

We have the whole "membership" system (like Edublogs) installed in our root dir (www.sitename.com), but want it moved to a sub-dir like http://www.join.sitename.com. How can this be done easily considering that I am no hardcore coder :slight_smile:? Or can it even be done?

Any help is appreciated -- thanks in advance.

Best regards,
Soreng