I think I understand what you're asking.
You'd probably want an on collision > spawn another object. Then once the second object collides with the wall, on collision, system > every X seconds, spawn the object.
Something like this. I didn't test it cuz I don't have time at the moment to build the whole thing, but in theory I think this should work, maybe with a little tweaking for your specific scenario.
(also apologies for the random objects, they're just stuff from my game)
EDIT: Dunno why the image isn't showing up, here's an Imgur link