Hi there Simon,
If I understand correctly where you talk about one engine per remote, are these both engines in the same consist? If so what you will want to do is create a Lash-up in the remote and add each engine you want in that lash-up then give the lash-up a name. Then when you select that Lash-up name (it will then be it's own engine ID in the remote) it will start both engines up at the same time and control both (or more) all with the same remote commands. Is that what you meant?