Siman 130

Our sages, of blessed memory, said in Berakhot (55b): One who sees a dream and does not know what he saw—let him stand before the kohanim at the time they ascend the duchan and say as follows: "Master of the Universe! I am Yours and my dreams are Yours. I have dreamed a dream and I do not know what it is. (May it be Your will, Hashem my God and God of my fathers, that all my dreams regarding me shall be for good.) (In the Gemara this is not present.) Whether I dreamed about myself..." until "for good." And we conclude "and guard me" (corresponding to "and guard you"), "and be gracious to me" (corresponding to "and be gracious to you"), "and favor me" (corresponding to "peace"). And it is implied from this that specifically when he does not know the dream does this avail, but when he knows—he specifically requires the "bettering of a dream" (and so wrote the Maharsha). And it appears that one should conclude simultaneously with the kohanim, so that when the congregation answers "Amen," it will apply also to his prayer. For "Amen" is very effective for his prayer to be accepted, as per their statement, of blessed memory: Greater is the one who answers "Amen" more than...

In the Gemara it is stated: And if not, let him say this: "Mighty on high… may it be Your will that You place upon us and upon all Your people the House of Israel… peace." And it appeared to me to interpret "and if not," meaning: that he did not manage to say the "Ribbono shel Olam" before the kohanim turned their faces, he should say "Mighty on high" (and it appears to me that this is what the Ma'adanei Yom Tov intended, see there). But the commentators of the Shulchan Aruch interpreted: "and if not," meaning: when they finished the "Ribbono shel Olam" and the kohanim still had not finished, he should say this as well (Taz and Magen Avraham). And according to this, the phrasing "and if not" is not precise. And there is one who interpreted "and if not," meaning: that he does not have the strength to say the length of the "Ribbono shel Olam," he should say "Mighty on high" (Eliyah Rabbah in the name of Agudah).

And know that our custom is that after the kohanim turn their faces, they say "Adir BaMarom." And this does not follow according to our version in the Gemara, but rather the custom is built according to the version of the Rif and the Rosh who read as follows: And when the kohanim turn their faces, let him say..., see there. And also our custom is that everyone says the "Ribono Shel Olam" even one who did not dream, because we do not ascend the duchen except on Yom Tov. And if not now—behold they will never say it. And perhaps they hold that this prayer is effective even without the day of the dream. And our teacher, the Rema, wrote that in a place where they do not ascend the duchen, he should say all of this at the time the sheliach tzibbur says "Sim Shalom," and he should finish together with the sheliach tzibbur so that the congregation may answer "Amen." Thus far his words. And if he saw that he would not be able to finish with the sheliach tzibbur—he should begin at the time the sheliach tzibbur says "Yevarechecha" (Magen Avraham). But he should not say so every day (Taz).