The only possible way I can think of (this doesn't mean there isn't any other way) is to have this in your whtlist.txt.
Quote:

Nick1 .
Nick2 .
Nick3 .
Nick4 .

It doesn't matter what the symbol after the "Nick1-4" is, as long as there is something after it. The reasoning is because when you use $read(file.txt, s, name-to-search) it will reply with the remaining text after, as said in the help file.

Quote:

//echo $read(info.txt, s, mirc)

Scans the file info.txt for a line beginning with the word mirc and returns the text following the match value.


This is the only way I see it being possible, of course once someone else posts some other way of doing it, i'll feel stupid, lol.

Code:
on *:NOTICE:*:?: {
  if ($read(whtlist.txt, s, $nick)) {
    echo -a User is on list.
  }
  else {
    echo -a User is not on list.
  }
}

I hope this has solved your problem.