I think you are headed in the wrong direction. UF_PASSWD_CANT_CHANGE is part of the UserFlags property of the user account.
See: AllFlags() - Test to see if all the flags tested are set
UsrMustChgPwd() - Force a user to change password at next login This second link will give code very close to what you need. You can also use the WinNT:// provider if you desire.
