virtual functions: can i call a derived class function, if isn't defined?

[Cambalinho]

on base class we have:
virtual void Hello()=0;
on derived class we have:
void Hello(); //not defined
here i will get 2 errors:
1 - "undefined reference to `b::Hello()'";
2 - "||error: ld returned 1 exit status"
can i avoid these error without define the function?
(if i don't use 'virtual', on base class, the function called will, always,called the base function instead the derived function)

[Peter87]

You need to define the function somewhere, otherwise, what's the point of it?

[Cambalinho]

i'm sorry, is only for see if i can create a global macro for the functions that i can use.
(yes it's, too, about that 2 macros that i created)