You've put your question in the wrong category, and it's not marked as a question!
Edit your post and do both those things, and you will get answers I'm sure!
As for your question, you can do this via scripting. ScriptFX have a container module called "soft bypass" meant exactly for this kind of thing.
If I have a spot of free time I'll make an example.
By the way, are you wanting the routing of A and B, to be parallel or series? Is one supposed to feed the other, or be completely separate? Because that will require setting up a bit of routing too!