class Base {
public:
	virtual ~Base() {};
	
protected:
	Base();
	virtual bool operator!=(const Base &that) const;
}

class Derived1  : public Base {
public:
	Derived1(char c) { myc = c;};
	~Derived1() {};
	
	bool operator!=(const Derived1 &that) const {
	
	return myc != that.myc;
	}
private:
        char myc;
}


class A {
public:
	A() {};
	void function(Base *that) {
		if (*that != *myV[0]  && *that != *myV[1]) {
			//do something
		}
	}
	
private:
	Base *myV[2];
}

client.cpp
#include "A.h"
#include "Derived1.h"

int main() {
	A my;
	my.function(new Derived1('a'));
	//my.function(new Derived2(1);
	
	return 0;
}