I do not think there is provision for seperate Desktops in sses - but may be wrong.
For seperate desktops you need either:-
Multidesk http://www.quasarbbs.net/cristiano/mudesk.html, and maybe sses if the 2 packages interact OK,
WPSac - Workplace Shell Administration http://www.nbsoftware.de/sw_wpsac_en.htm which may have all the necessary security administration builtin, the readme states:- WPSac - Workplace Shell Access Control is a tool
that restricts access to the workplace shell to
users with a configured user id (comparable with
the WinNT logon). It also enables the administrator
to restrict access to objects inside the workplace
shell of a user. Users may share a workplace shell
or use their own. Also it is able to logon to other
tools or the LAN via the "Single signon feature".
Multdesk requires a reboot to login a new user, not sure about WPSac.
Multidesk and sses are free, not sure of the price of WPSac.
Hope that helps.