A multimacro key (probably the three buttons just below Mute and Last) can have a series of macros assigned to it. If you've assigned 3 macros to it, successive macros will be executed on each press of the multimacro key. 1st press-macro1; 2nd press macro2; 3rd press macro3; 4th press macro1.... This feature is mostly useful to scan through "favorite channels".

I think you should be able to define the following macro:
995 (two blinks)
button "Blue" (as an example)
button Audio
button [whatever receiver discrete On is assigned to]
button TV
button [whatever TV discrete On is assigned to]
button Audio
button [receiver discrete input--probably the digit buttons on 1374 control some inputs]

Here I've interposed the TV power on signal between receiver power and receiver input selection. That may be enough time for the receiver to wake up and then process the input command. If it isn't enough time, you may want to add a delay. At our house, we find that the receiver remembers which input was last selected, and most of the time we'll want the same input again. So I haven't put in any special delay-- if the receiver doesn't switch to the correct input, just press the macro button again.