Retracting a Blessing after Third or Fourth Word

If you start an incorrect blessing:
  • If you have said the third word (God's name), say
    lamdeini chukecha.
  • If you have already said the third syllable of the fourth word (elohei…), say
    Yisrael avinu mei'olam v'ad olam.
  • If you said more than the third syllable of the fourth word, say
    Baruch shem kevod malchuto l'olam va'ed.