packet sniffer(filter)

dear all
i have to develop a packet sniffer in vc++ with winpcap this sniffer should capture incoming and outgoing packets.
also the capturing process should be filtered based on process id i.e if the user gives a process id as input than the incoming and outgoing packets of that process should only be captured and saved to a log file please help me or give me the related links thanks in advance .

regards
sudha

Check out --> http://www.codeproject.com/Purgatory/Sznyfer.asp