How to edit Block Triggers for my mod?

 Hi guys!

I've got a question about the triggers for my mod, because i'm trying to trigger an event when only the PLAYER'S HEAD hits de block and not the other part of its body.

I've got my trigger which is quite working as I want but I can't manage to get it work only for the players's head or the top of its head (like the helmet).

I have a video here to show you how it's working right now, but now if someone can help me about that! :)

https://www.youtube.com/watch?v=1I_zuE5V3LI

Thanks!