how to pass class member address to a function so that assign it to a class member pointer inside the function?

Question

given a class like

class Person{
public:
    int age;
    string name;
    Person( int i, string n ):age(i), name(n){}

};

If we have a global class member pointer, we can do something like this:

int Person::*class_member_ptr;
class_member_ptr = &Person::age;

But what if we wanna do the same thing in a function, what is the function signature, and how do we pass Person::age into this function such that:

void func( Person::age ){

   class_member_ptr = &Person::age;
}

the data type of the argument in the func() is wrong. it can't be compiled. How do we make the data type of the argument right?