Detecting connected PC in LAN

I've a hard time now... hope your guy can help me...

For instance, I intend to develop any application that install either on the WinNT/Win2K
Server (running in DHCP mode) or any workstation in LAN environment. And the prime task
for my app is to detecting the following items:

• The instance of any PC connected to the domain.
• The IP address of the remove PC.
• Connected date/time.
• The instance of any PC disconnect from the domain.

*Assume my network environment have 500 to 900 network point and for most of the time
only 30% to 40% of the network point is occupied.

Can this be implement by using the ADSI object or anyone can recomend any good reference
URL, sample code or app for me.

Thanks in advances.

regards,
Chris.C