If I am praying next to an elderly person who I know is somewhat dependant on my help to find the place in the prayer book, at what points in davening may I silently direct him to the correct page/place (eg by turning the page in his siddur or pointing to where the chazzan is up to)? Can this be done while I am still saying shmona esrei if the chazzan begins his repetition before I am finished? I expect I can at most if not all other points in davening, but am open to hearing otherwise. Does it matter if someone else might come over to help if I don't?
Partially inspired by: Am I allowed to interrupt someone in the middle of Shmoneh Esreh if my question is related to davening? though in my case the help is going the other way.