Has anyone found that they can't use a [device Ndevice( message to choose video devices with [pix_video]?

I can't get it to work - am I being thick? I've been sending [device 0( etc. ('device' + no.), but doesn't really seem to be doing anything - if I want to switch between devices, I've had to use [dialog source( and change there each time.

Hope someone out there knows what I'm missing.