can we define a comment?

["Eric Fisher" <joefoxreal@xxxxxxxxx>]

hi,
Anybody knows that if we can define a comment? For a statement such as,
  COMMENT this is a comment.
will be preprocessed as,
  // this is a comment.
or something valid and transparent to the compiler? Of cause we can't
directly use,
  #define COMMENT //

Thanks.
Eric.