MB 29: He should not interrupt - If he did interrupt for this [being called to the Torah] and also [if he interrupted] for Kaddish or Kedushah, then he is considered like one who deliberately spoke [during the Amidah], and according to the opinion of those Rabbis that in that case [of deliberately speaking] he should go back to the beginning [of the Amidah], so also here he should go back to the beginning. But if he believes that it is permitted to interrupt [for Kaddish, etc] then he is like one [who speaks] unintentionally and he need not go back to the beginning, as mentioned above [in MB25]. But if they called him to the reading of the Torah and he was standing at the point just after the Amidah, even if he had not yet started "Elokai Netzor", he should interrupt and go up [to the reading of the Torah], but he should be careful first to say "Yiheyu LeRotzon Imrei Phi VeHegyon Libi LeFonecho Hashem Tzuri VeGo'ali" beforehand.
Stephen Phillips stephenp@cix.compulink.co.uk
sha104.08
Siman 104. That one may not Interrupt during Prayer (cont.)
104:8. (30) After one finishes the Eighteen Blessings, before saying the additional prayer "Elokai Netzor" (My G-d, Guard...), one is permitted to respond to Kedusha, Kaddish, and Barchu (and see later in Siman 122).
MB 30: After one finishes - Meaning when one has also said "Yihyu L'Ratzon..." (May it be favored...) before "Elokai Netzor," for if not it is forbidden to interrupt, as we will see in Siman 122 - and this is what the Rema is hinting in what he wrote, and see later in Siman 122.