samba - Jun 2015 - User access to subfolder of restricted share

Hello List,

I am relatively new to Samba.  I've recently installed an instance on 
our server (local authentication, utilizing libpam-smbpass), and have 
successfully created a number of employee accounts.  The setup we're 
going for is to give all employees access to a general "projects"
folder
(all have access to all items in the share), but with the ability to 
give piecemeal access to subfolders within this share to non-employees.

For example, if we need to hire a contractor, we'd like to be able to 
give them an account, such that:

     (DENIED) \\server\projects share
     (ALLOWED) \\server\projects\funproject

In the context of Windows-dialogs, (among many other details I've tried) 
I've set the permissions on the \\server\projects share such that only 
members of the employee have access:

     Group or user names (for \\server\projects):
       - employee (Unix User\employee)
       - employee (SERVER\employee)

I thought it would be as simple as then adding a contractor's username 
to a subfolder:

     Group or user names (for \\server\projects\funproject):
       - employee (Unix User\employee)
       - employee (SERVER\employee)
       - somecontractor (SERVER\somecontractor)

and somecontractor has modify access.  However, when I try to map that 
as a network drive ... no luck.

     Map Network Drive
     Z: -> \\server\projects\funproject (with: somecontractor/password)

Any insights much appreciated!

Thanks,

Kevin