I would answer with a question; why? (i.e., please explain your problem and not your solution)
Stefano,
I appreciate your approach, because I know you want to be sure you are solving problems and not providing misguided solutions. I see that often, and I know sometimes people are affronted by the question and think "Just tell me what I want to know." Well, sometimes we don't know what we need to know.

In this case, there is a user who needs to have access to the server to upload and store files, but we can not have them putting things on there in a location not visible to everyone else. It is truly a groupshare only type of scenario. We noticed a lot of space disappearing on the server only to find out they had somehow turned on Windows Backup or Previous Files or whatever they are calling it now, and they had not only uploaded some 250GB to the public i-bay share, but they had over 500GB in their home folder for which nobody could see. I was called in to find out where all the missing space was because they were running out and couldn't find the files.
I am going to work with them and advise that the file server is not appropriate for this function, they should have a portable USB drive on their laptop for the Windows backup feature, and that only truly shared items need to go on the file server. And even then, if something is truly archival in that you expect to never use it again, you might find a better way to do that rather than leave it on the server.
The reason for the more brute force approach to wanting to shut off his access to the home share is that very often policy simply can not be followed by some people, and I have no authority over them to force or even strongly encourage compliance, so the only recourse is to be sure it can't be done in the first place.
Knowing that there is nothing in the GUI to do this, I will look into the Samba configuration options.
Thanks,
Steve