force nm to use a connection

[Jérôme PRIOR <ast3roid gmail com>]

hello,

I'm looking for info to force nm to use a connection instead of "Auto
eth0". I explain :

  at home I need a static IP, with special DNS, ... So, I created a
  connection called `home` with those parameters. Works fine when I
  activated it manually.

  When I'm outside, I need `auto eth0`.

How can I tell nm "when I'm at home, connect me via `home`, even if
connect me via `auto eth0` ?

I try to pla with "automatic connection" but of course, if I put `home`
as auto, and `auto eth0` as no-auto, when I'm outside, `home` is up.
And inversement.

Thank for show me the way.