Use tags. Tag the Box “Triggerbox”, say.
For example, for the OnBeginOverlap for the ball, do an “ActorHasTag” check and put “Triggerbox”. Feed this to a branch node. Now OnBeginOverlaps will only fire (from the True pin) if the overlap occurs with an actor who is properly tagged.
I use these all the time for meshes which interact with my player character differently than NPCs, for instance, since both are on the Pawn collision channel.