You can't. And you shouldn't, even if it was possible. It makes no sense - why would you want to do that? If M1 and M2 are specific to B and M3 specific to C, then implement M1 and M2 in B and M3 in C.
It would violate the principle of
polymorphism[
^]: A subclass should behave like the baseclass if it is being used like the baseclass. If a B-class doesn't have access to M3 then you wouldn't be able to use it like an A-class.