Client Machine Logging to Distant Server

I have a LAN with a Compaq ML 350 server configured as a BDC with aprrox 100 NT4 Workstations. This LAN is connected to my corporate office with a 256 KB Frame Relay connection and that’s where my PDC resides along with few other BDC’s. I use Logon scripts and it gets replicated to all the BDC’s. My problem is that most of the WKS are running their Logon Script from my PDC or some other BDC from my corporate office rather than the Local Server. Can anyone tell me why it’s happening and how can I force it to look for my Local Server ?

Thanks