Q. What happens if someone during the 30 days of establishing a chazaka for saying mashiv haruach in the amida, (see prior question 2428), forgot to say it once. Does he have to start counting full 30 days again from that time?
A. Horav Shlomo Miller’s Shlit’a opinion is that he does not need to start all over again with the count of thirty days, if he forgot to say it once or several times, he just has to add that number of occasions missed to complement the correct total number of tefilos said in thirty days.
The Rov added that the above applies only to when the tefilos where mashiv haruach was omitted is less that half of the thirty days required.
Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a