Well if i got it right, it's about some game, so maybe you could try assigning a sort of profile to each player. Because you dont know the number of players or who the players are each time, i would try putting them in a plain text file and tokenize the information i want for each player, including the nickname, each time a new player shows up:

In my example i want nickname, join date and score (which initially is zero) and i separate them with ^ which is $chr(94):

on *:JOIN.......bla bla {
write "players.txt" $+($nick,^,$date,^,0)

Now, the next time the same nick enters the game, i can recall their nick or score or anything by accessing the file:

var %mask = $+(*,$nick,*)
var %search = $read("players.txt",w,%mask), %line
if ($readn) { %line = $readn }
else { halt }
var %nickname = $gettok($read("players.txt",%line),1,94)
var %score = $gettok($read("players.txt",%line),3,94)

And then use it as needed:

/msg %nickname Hello again!