1. When in the middle of praying the Amidah, one should not stop in order to answer “Amein Yehei Shemeih Rabbah Mevarach” nor to say the correct responses to Barechu and Kedushah. Instead, he should be quiet and listen to the repetition of the cantor, whereby he will fulfil his obligation by using the rule of Shomea Ke’oneh (one who listens is like one who said it himself), and it is nevertheless not considered having interrupted. (Shulchan Aruch and Mishne Berurah 104)
2. If when in the middle of praying the Amidah he was called to read in the Torah, he should not go. However, if has already finished the main part of the Amidah, but has not yet said Elokai Netzor, he should immediately say the verse “Yiheyu leratzon etc.” and go to read in the Torah. (ibid)
