Regarding Birkas Kohanim here in Eretz Yisrael: Often due to two scenarios I have to accelerate my Shmone Esrei in order to be able to duchen timeously 1. The chazaras hashatz is started very quickly - one could still be in the middle of his personal Shmone Esrei 2. The chazan davens the chazaras hashatz very quickly One of my sons was told by another Kohen that one could stop his Shmone Esrei wherever he was, go to duchen and then continue where he left off. Is this in fact so? I could not find any mekoros for this. Could one possibly at least finish the Shmone Esrei until the last brocha [Sim Shalom] and then go up to duchen? Your comments and suggestions would be greatly appreciated. A very big thank you.
The Mishna Brura in Hilchot Nesi'at Kapai'im (סימן קכח ס"ק ק"ו) discusses your dilemma at length. The Mishna Brura says that if there is only one kohain and he is in middle of Shmone Esrei, then he should interrupt his Tefilla and go to duchen in order not to cancel the Nesia't Kapai'im. If there is another kohain who will say the Nesi'at Kapai'im, the one still in the middle of Tefilla should not interrupt his Tefila unless he was specifically told to go up for Nesi'at Kapai'im. In both these cases when the Chazan reaches "Retzeh" he should shuffle his feet a bit in order to indicate that he is on his way. (See סימו קכ"ח , סעיף ח,where it is specified that the Kohanim must start to move to the "duchan" when the Chazan it at Retzeh. ) However, the Eliyahu Rabba and the Yaa'avetz have their reservations and say that in either case the Kohain should not interrupt his Tefilla, since Chazal upheld their position of not interrupting Shmoneh Esrai even if Nesi'at Kapai'im is not to take place. However, the Ya'avets also said that if the kohain in his Tefilla reached "Birkat kohanim" at the same time as the Chazan it is not considered an interruption since it is as if he had reached "Sim Shalom" and he may do Nesi'at Kapai'im. This is also with two stipulations 1. If he assumes that he will reach "Birkat kohanim" at the same time as the Chazan, when the Chazan reaches "Retzeh" he should shuffle his feet a bit as we said above. 2. The Kohain who has to interrupt his Tefilla should should be able to go back to his Tefilla where he left off after Nesi'at Kapai'im without loosing his concentration of the Shmoneh Esrei. For if not so, he should continue his Tefilla without interruption.