What I thing It is works for me with a network drive and VirtualHost like this:
<VirtualHost *:80>
ServerName my-site-number-3
DocumentRoot //192.168.0.11/public/sites/site3
ServerAdmin
webmaster@nowhere.net<Directory "//192.168.0.11/public/sites/site3/">
Options Indexes FollowSymLinks MultiViews
AllowOverride all
<RequireAny>
Require local
Require ip 192.168.0
</RequireAny>
</Directory>
</VirtualHost>
192.168.0 is the root of ip's of employees PC.
This need that the network drive must be mapped to the server PC with an IP adress