The N900 has an option to connect automatically to wifi when available. Does anyone know how to customize this? Here is what I want:

1. My home internet is faster than 2G but slower than 3G, so I want it to switch to wifi only if I have a 2G connection.
2. I have unlimited data in my service plan, so I want my N900 to automatically connect to 2G/3G when it loses the wifi signal.
3. If it is connected over 2G/3G and I lose reception, I want it to automatically re-connect when I get reception back.

Does anyone know how this could be done? Or, at least, where the relevant information is stored, so I could write a script to do this myself?