[Avodah] birchot hamitzva

[Eli Turkel]

Micha writes
<<My father taught me to avoid saying "amein" to the birkhas hamitzvah
on Hallel, or on birkhos hamitzvos that one plans on making oneself.
Something he learned from RYBS.

Why aren't you yotzei the chazan's berakhah? You couldn't be, or else
your berakhah is levatalah? Mitvos einum tzerikhos kavanah, so you
can't rely on not intending to be yotzei. Rather, to avoid being
yotzei, one must have negative kavanah in mind -- specific intent not
to be yotzei.

Who wants to practice such negative kavanos? Better to say the
berakhah with the chazan and avoid the issue.>>

This is discussed at length by poskim with regards to sefirat haomer.
The normal minhag is that the chazan first recites the beracha and then
everyone repeats it. The poskim argue why this is not a beracha le-vatala
since one is yotzeh with the chazan. Among the suggestions is to have
kavanah not to be yotzeh for the chazan to have in mind not to be
motzeh.
As Micha notes every suggestion has its difficulties

kol tuv

-- 
Eli Turkel