logon script

Hi,i am using nt 4.o server with sp6,and on workstation ws 4.0 with sp 6,we have PDC located across wan in another office and BDC in our local office,my problem is when ever user logs in they get autentication from PDC which is on WAN,how do i forceuser to get autentication from BDC which is on LAN,
can anyone help me in this regards.