Sorry. The above is based on two way feed back. This is how I would do it if using flags. First you would have to create the variable "flag"you want to use. Say for example you call it " System Power On". You would put a programming command in your source select macro called "set flag" and select your variable. On your activities buttons is where you would use the command " test flag" which creates the conditional. On system power off you would put a command in that macro called "clear flag" and select your variable. So basically an activity button would look like the following:

If flag " whatever you call it" is set:
Select " input whatever on your tv"
Select " input whatever on you receiver"
Else
Run the entire source select macro
Set flag "whatever you named it"