You have the right idea, but the wrong syntax. Here's the complete syntax for programming an advanced code:

[SETUP **] 994 ** {dev1} SETUP nnn {dev2} button **

So, let's say you're not using the transport keys in P&P mode for anything and this is where you'd like to store all these special selector codes. Let's program the REW button to select the DVD input.

First, program the VCR button to code 0522
Then, using the above syntax, you would do this:

[SETUP **] 994 ** VCR SETUP 227 P&P REW **

You get the idea?
Rob.