Dear Rabbi, Thank you for your prompt answer, I’ve got another question. If on Shabbat somebody is walking to a family Kidush where hes presence is important, and pases by a small shul and is asked to join in to complete the Minyan, is he obligated to do so? If yes can he stay by the door and seek actively somebody else to replace him?

A. According to many Halachic opinions the ruling of “Ein maavirin al hamitzvoth” or not to bypass a mitzvah is a biblical injunction (see Tos. Yumah 33a & b, Nishmat Adam 13,2 and Areah Derabanan 1), and once a person has a mitzvah in front of him to perform, he has to engage in that mitzvah, even if he forfeits a greater meritorious act, as in Pirkei Avoth (2,1) “Be as careful with a minor mitzvah as with a major one, for you do not know the rewards of the mitzvot.”. Accordingly Horav Shlomo Miller Shlit”a advices to partake and complete the minyan as requested. Yet, it is permitted to seek and engage somebody else to replace him.
Rabbi A. Bartfeld as adviced by Horav Shlomo Miller Shlit”a