How would I expire logins

["Suheyl Husain (Faculty)" <shusain ssuet edu pk>]

I am using RH 5.0 Kernel 2.0.32 & 2.0.34 ... and using PAM_smb for
authentication ... I wanted to expire some logins on linux systems but not
on NT ... I have tried placing [x] in the password box ... but it seems to
to accept passwd from NT ...  if I change the passwords ... it
authenticate from either NT or Linux itself ( depending on what password
you have used ) ... is there some decent way to solve this problem 

Suheyl