samba - Oct 2006 - How to handle domain logons if users using same accountname are logged on the same time?

Hi,

I'm working at a small office.
I'm running Samba 2.x for about a year without any problem, it's working
absolutely GREAT and the community kicks ass :)
We don't have too many machines so about 6 Users use about 3 PCs to do 
similar tasks.
I just setup samba latest 23c-1 as a DC because we got some more 
machines, and everything's fine. Except when the same account is used on 
multiple machines the same time, there are problems of course.
It simply doesn't make sense to me to create different accounts if users 
who are using these machines change frequently and they all do the same 
tasks.. I even couldn't control whether they login as acc1 or acc2 on 
machine1 or 2.
Let's say account xyz is logged in on two machines the same time.
If a user saves a file on the desktop on machine 1, and the user on 
machine 2 logges off after user on machine 1 logges off it happenes that 
the changes done to a location like "desktop" are not synchronised 
properly on the server share..
How should I handle this?
Deny all access to "Desktop"?
Also it would be a problem if an application is installed on a machine 
using the same account which is currently used on another machine.
Would I need to make sure each account is used only one time at once?
Sorry, these are total newbie questions.. I used the official samba 
howto "practice" tuts, but these questions aren't covered it
seems..
I really don't know how I should/could handle this.

Could someone plz point me to the right direction?
Would be very appreciated and very very nice.

Thnx,
Regards,
Michael Rignaz

I'd especially like to know how to force users to store their files on 
the home share rather than on "Desktop", without mounting the desktop 
path on the home network share.. How could I deny write access to the 
Desktop globally?

Thnx a lot
Regards,
Michael Rignaz