XP SP2 local password policy enforcement on existing accounts?

We have a Novell workgroup environment where we use Novell's Zenworks
management tool in order to maintain the local workstation accounts.
Currently we have no Windows password policies being enforced at the
workstation level. Password criteria is dictated soley by Netware. We
would like to enforce certain criteria (maximium password age, length,
complexity) on the workstations themselves using local group policy.
In my testing thus far, it does not appear that the local policy takes
effect on workstation accounts immediately after it's pushed. Is this
true? If so, when does the local workstation accounts adhere to this
policy? When the password is changed to something else? What we want
to make sure is that the two policies, local and Netware do not
conflict causing a user not being able to log in.

Thanks in advance.