Exluding local traffic using ‘Local Host Monitor API’

Goal:
I’m trying to capture all traffic that is transmitted to an external address or received from external address – No inter-process communication via sockets.

Question:
I can see how you can include just remote traffic you want, but I’m not sure how setup a filter to block all traffic that is not Tx or Rx externally from the host computer (i.e. block inter-process communication via sockets).

Setup:
The computer I’m targeting my application for has:
1 PPP connection (IP changes every few minutes to an hour)
1 WIFI connection (IP changes every few minutes to an hour)

Complications in just blocking loop-back address:
I think that the remote address will be the loop-back address 90% of the time, but what about the case when the remote address is assigned NIC address. I don’t want to capture local traffic / inter-process communication.