Hello, Roddy!
In short, yes, this is possible. In your blueprints, you should have an event that is called when objects collide. That event is connected to the result of the collision - perhaps the characters stopping or ‘bouncing’ back. You could put a ‘branch’ between the collision and the result of the collision, and in that branch check that the collision is with the other object. That should allow you to ignore collisions in one direction, and only with one pair of objects.
Good luck,
Jonathan