Code:
msgx {
  var %xs = 1 
  var %max = $lines(mp3chans.txt)
  while (%xs <= %max) { 
    %xme = $read(mp3chans.txt,%xs)
    scon -at1 msgx2 %xme $!1-
    inc %xs 1

  }
}
msgx2 {
  if ($chan($1) == $1) {
    .privmsg $1 $2-
    .echo -i25 $1 9[ $+ 11 $+ $timestamp $+ 9] [ $+ 11 $+ $1 $+ /11 $+ $me $+ 9] 11 $2- 
  }
}


Didnt try it but I think its right, what its ment to do is just issue the command /msgx2 channelname $1- to each active server connection , then let the alias check if your on that channel, if so do the deed.