I'm not 100% sure the device multiplexer works properly... or else I'm using it wrong
Special Function
DVD Phantom7 Multiplex DVD:code1
DVD Phantom8 Multiplex DVD:code2
Macros
DVD     Dev_DVD;Phantom7;Set_Chan;Set_Trans;Set_PIP;Set_Menu;Set_Other
Shift-DVD Dev_DVD;Phantom8;Set_Chan;Set_Trans;Set_PIP;Set_Menu;Set_Other
So I press DVD then Power and my DVD player powers up
Then I press shift-DVD then Power and the BluRay powers up.
So far so good.
I then press AUD to select my Audio Receiver... press Volume Up... nothing happens.  The right LED flashes but power doesn't change.  Press POWER and the Aud LED flashes... but the BluRay turns off.  So either I'm doing something wrong, or the multiplex  code isn't quite right.
But I worked out another solution to my problem; I only need 4 primary functions from my audio device in every-day usage (vol-up, vol-down, mute, power-off) and secondary device select functions.  I mapped the four primary functions to my TiVo device (vol+/vol-/mute/phantom2) and the device select functions are in each device upgrade as part of the "external functions" tab.  (Which is a nice update from the old IR.EXE I learned all those years ago!)
So I think I can work around the 5 device limit without needing the multiplex addon 
