Talking [Q] How to tether WiFi connection via USB

Hi! Greetings and so on...

I have an old backup phone running Cyanogenmod 7.2 that I very occasionally use. Now, however, I got a new PC (actually, second-hand) which is great, but it does not have a WiFi card.

I was thinking that I could connect that old phone via USB and use it as a WiFi card of sorts.

However, it seems that tethering the phone will only share the mobile data plan, and not the WiFi connection.

Is there some way that I can thether the phone to share ONLY its WiFi data, and not its mobile data? I could not find a Play Store app that does stuff like this...