Ensure the user creates instance of a new subclass

Question

Let's say there is a base class

class Base
{
}

and the user has created a new subclass

class NewDerivedClass : public Base
{
}

There is also a enum for all the subclasses:

enum SubclassId
{
    Derived1_Id,
    Derived2_Id,
    ...
    NewDerivedClass_Id  // User has to add this line
}

Now, there is also a factory which creates derived instances based on the SubclassId:

class SubclassFactory
{
    Base* CreateSubclassInstance(SubclassId subclassId)
    {
        switch(subclassId)
        {
            case SubclassId::Derived1_Id:
                return new Derived1(params);
            case SubclassId::Derived2_Id:
                return new Derived2(params);
             ...

            // User has to add the following lines:
            case SubclassId::NewDerivedClass_Id:
                return new NewDerivedClass(params);
        }
    }
}

1. How can I force the user of my Base class to add new Id in enum?
2. How can I force the user of my Base class to create it's instance in SubclassFactory?

In the best case I would like to see a compile-time error. Unit test solution to this problem is also acceptable.

---

Additional information.
1. Users of the Base class create new subclasses in the client side.
2. My code operates in the backend. I get the subclass id remotely and use Factory to make instances of the subclasses created by client programmers.