Mitch,
Hard keys are assigned codes on a global basis as well as a local(device) basis. With this in mind, if you have both a cable device as well as a TV device, which may look identical, this would allow the assignment of a different IR code for the channel up/down keys depending on which device has been selected.
I think this solves your problem.
Of course it probably also makes sense to send the ANT select on the way into the device menu.
As a PC software beta tester, I'm not sure if this can be done with the on screen software or not, but it definately can be no problem with the PC software.