Here's what I sent to your email. Posting here since it may give other users an idea. It's not a fully fleshed out method, but I think the concept is sound.
If you only want to be able to pass backwards, you can use a behaviour like calculate direction (may be renamed to calculate angle, cant remember).
to figure out where the team mate is in relation to the player. If they are behind, then turn on the "pass button" behaviours.
This concept requires some math and calculations to get right. But I think that is one way that may work. Or at least it's an idea on how to get started.