Yes, it is no problem to do this. What you should do is use the "List Group" feature.. so that each customer has a unique List Group that specifically "includes" ony their folder.
So user "Florida" would be assigned to a List Group called "Florida". The Florida list group then is set so that all only the "florida" folder is "included".
This way, that's the ony folder the user will be able to see.
Then create the user so that their "starting folder" is your website root folder, which is where the "shared" calendar file should be located.
So when the user logs into Snippetmaster, they'll see the calendar file for editing, and they can navigate into their "florida" folder to see the rest of their files.
I hope that all makes sense?
Let me know how things go.