After Bracha of הודאה
19. Stopping to pay attention. Many people, if they are davening Shemoneh Esrei and reach the end of the bracha of הודאה with the shliach tzibbur and are now hearing Birkas Kohanim, pause, listen, and pay attention to Birkas Kohanim (חזו''א, דינים והנהגות ח''ג סי' ט''ו, שו''ת אג''מ או''ח ח''ד סי' כ''א, שו''ת שבט הלוי ח''ג סי' ט''ו, מו''ר בשו''ת שבט הקהתי ח''א סי' ע''ט).
20. Saying Amen to the bracha of Birkas Kohanim. Some poskim hold that a person in the middle of Shemoneh Esrei, after the words “ולך נאה להודות,” may answer Amen after the bracha “לברך את עמו ישראל באהבה.” They hold it is not an interruption in Shemoneh Esrei since the bracha is related to the spot in davening he is currently at (ט''ז סקי''ד, פמ''ג משב''ז שם). Others hold he should not answer Amen (ב''ח סי''ט, פמ''ג שם, א''ר סקל''ח).
21. Amen after the three pesukim. However, most poskim hold one may answer Amen to the actual brachos of Birkas Kohanim, i.e., after each of the three pesukim, because he is up to that spot (שו''ת שבט הלוי ח''ג סי' ט''ו, ס' כה תברכו עמ' תק''ד).
At a Different Bracha
22. Some hold that if one is at a different point in Shemoneh Esrei and hears the shliach tzibbur reach Birkas Kohanim, he should pause, listen, and pay attention to Birkas Kohanim since a Yisroel also has a mitzva to receive the bracha (שו''ת אג''מ שם, שבט הקהתי שם). Others hold one should not pause to listen to Birkas Kohanim, and he is included in the bracha even if he does not pause to listen (שו''ת שבט הלוי, כה תברכו).
23. Answering Amen. Even if one follows the opinion that he may pause, he should not answer Amen after the bracha or after the three brachos of Birkas Kohanim, because he is not up to that point, so it is considered an interruption (כה תברכו).
