|I'm having a hard time understanding exactly what you are asking but this is how you set this up.|
Create a folder called 'Users'. Share the folder with Full Control Share permissions for Everyone. Set the NTFS permissions so that only Domain Admin has access to the 'Users' folder.
Create the account or set the Home folder, Connect path in the Profile tab of the account to the drive letter you want and a path of \\servername\Users\%username%.
If they log off their computer and back on using their domain account, the folder should map. Make sure another device, like a USB or media reader isn't trying to take the same drive letter as the one you assigned for the folder.
Let us know how that goes.