R Eli Mansour brings the Shulchan Aruch (OC 109:2) that
if a person comes late to the synagogue and misses the congregation's
silent Amidah, he can still earn the merit of praying with the
congregation by reciting the Amidah word for word with the Chazan.
When he and the Chazan complete the Beracha of "Mechayei Ha'meitim,"
he recites Kedusha together with the Chazan. He then continues "Ata
Kadosh" with the Chazan, and bows with the Chazan at the recitation of
After the Beracha of "Ha'tov Shimcha U'le'cha Na'eh
Le'hodot," he should stop and listen to Birkat Kohanim. He may also
answer "Amen" to the Beracha preceding Birkat Kohanim and after each
of the three verses of Birkat Kohanim (after "Ve'yishmirecha,"
"Vi'chuneka" and "Shalom"). He should not, however, answer "Baruch Hu
U'varuch Shemo" during Birkat Kohanim.