if (key == K_RETURN && FocusCtrl() == &jog.jog_pos_el)
    // Do whatever 

template<class T>
struct WithReturnCallback : public T
{
    Callback WhenReturnKey;
    virtual bool Key(dword key, int count)
    {
        if (key == K_RETURN) {
            WhenReturnKey();
            return true;
        }
        return T::Key(key, count);
    }
}