For starters, in WinPCap, you can define something called filter.
That filter filters out all the traffic except the type that you specify, so if you want to capture HTTP traffic only, I'd suggest you make a filter on TCP Port 80
or any other port you're using for HTTP.
Once you've captured these packets, you can check the payload of the TCP, parse the HTTP header and do whatever you wish according to your system's policy.
Check this link if you want to familiarize yourself with how to use WinPCap and how to use filters(in this example they're capturing TCP traffic in general, you should add to their filter "port 80").