I can connect my home PC to my office LAN via VPN connetivity over successfully,

however,

I cannot connect to my office LAN, when I attach my home PC to another home PC, directly with two network cards or with a hub.

Is ther anything I can do to establish a connection from my home to the office while being connected to my home LAN at the same time?

To temporarily solve the problem, I detach my ethernet cable from my computer.