switch user could be better

I'm experimenting running some things with a seond user. It's possible to configure a key (in my case "Pause", which seems I never ever pressed in my life an does nothing otherwise) to do "swtch user". However, you then have to select this user (which the is locked, although I never asked for a lock). Would there be any way to have a "move to the next user" function? As I only have two users, I fon't need a choice :) Thierry