Drive blueprint nodes when trigger box is empty?

hi i just have a quick question: im trying to set up a can game in VR where you throw a ball at some cans.
the cans have physics. i was trying to set a up a something like an inverted trigger box.
so that i can drive some nodes based on the box being empty.
i tried making the trigger box a variable in the level blueprint and then added an event onendoverlap.
the trigger box has a collision preset of overlapalldynamic and the cans are physics actors.
i was just testing it by printing a string to screen but it just doesnt print.
any ideas what the problem may be? or how to do such a thing easily?