Problem is, I don't think particles have collision boxes.
Ninjusk:
You could try using normal blocks. They'd be solid (and have code that detects collisions, like the cactus) but when the...creator of them dies (should be possible to detect) you trigger one of the blocks (doesn't matter which one) to set its metadata to a specific value, then on its next update, replace itself with air.
Then you can use that change in state to set the rest of them to do the same thing (think redstone, but without the signal decay). I use similar code in my phase blocks mod, which is open source.