I'm not sure how to work with the pick system in C2, but imagine something like that, you check if 1st block overlaps at offset Y -5 (choose your value) with 2nd block, than you check for 2nd block with 3rd block and so on. If all of this conditions are true, you have your 4 blocks. Can't help you much now, but that may lead to a solution.
i will try it and let you know if it work, thank you