Force logon to Domain ??

Anyone know of a method to force users to
use thier domain logon details when logging in to
a win98 machine instead of just hitting the Cancel
button.
All the 98 machines are members of an NT 4.0 Domain
and all users have domain accounts but no local accounts.
..
What I need is to deny them access to the machine unless
they actually logon to the domain.

upgrading to win2k or XP is still a long way off.