So all I need to do is set that function to static. Thanks.
However, I found that I also have to set every variables used in that function to static. That leads to making class B static which leads to unresolved external symbols from static B b[40][40] in another class. I'll try another approach.

No - you can access protected and private class members in a static member function. Consider:


class A {
protected:
int protectedBaseMember;

};

class B : public A {
private:
int privateMember;

static void StaticFunc(A* obj);
};


//static
void B::StaticFunc(A* obj)
{
B* b = (B*)obj;

//this is perfectly legal and accesses two non-static members of B
b->privateMember = b->protectedBaseMember;
}


A static member function can access any member of its class just like a normal member function, but has to do so through a named object rather than the this pointer. All you need to do is make sure the object is properly initialized and arrives in the static function through some means (doesn't need to be passed in as an argument).

class A is a button and class B is "Mine Button" in MineSweeper.

Actually the interesting thing to know is, how do the various B classes differ, and can some of them have several "functionIwantToPass" ?
Assuming they don't, here is a solution:
class A
{
virtual void action() = 0;
public:
void activate() {action();}
};

class B : A
{
void functionIwantToPass() {...}
void action() { functionIwantToPass() }
};

Sorry I you already knew, or if this is not suitable. But I think it is best to learn simple things first, before function pointers.