Marcello,
I was having issues getting your solution to work, it seemed to work well on my first block, but not on subsequent ones. Then I noticed that your formula only went up to row 100, and I had set-up my example to go over 200, like the OP described originally. So I bumped your row references in your formula from 100 to 1000, and then it worked fine! Nice job!
So, now the OP has both a formulaic and VBA solution to choose from.