Basically, the script asks you for a length to build a password, set here from 4 to 25 characters in length. The maximum length can safely be taken out to approx. 40 characters before locking the mIRC up.

;=====================;
;Random Key Generator ;
;    By Anthalus      ;
;Irc.FlirtUniverse.Net;
;=====================;

alias random.key.gen {
  :one
  var %len.max = $$?="Length of Password (4-25)"
  if ( %len.max < 4 ) || ( %len.max > 25 ) { goto one }
  :calc
  var %alpha.one = $rand(A,Z)
  var %alpha.two = $rand(a,z)
  var %alpha.three = $rand(a,z)
  var %alpha.four = $str(%alpha.two,2)
  var %alpha.five = %alpha.one $+ %alpha.three
  var %num.one = $rand(1,150)
  var %num.two = $rand(1,150)
  var %num.three = $calc(%num.one * %num.two)
  var %num.four = $int($cos(%num.three))
  var %num.five = $int($calc($cos(%num.one) * $tan(%num.three)))
  var %pre.final = %alpha.one $+ %alpha.five $+ %num.one $+ %num.two $+ %alpha.two $+ %num.five $+ %num.three $+ %num.four $+ %alpha.three $+ %alpha.four
  var %pre.final.two = %num.one $+ %alpha.two $+ %num.four $+ %num.three $+ %alpha.four $+ %alpha.three $+ %alpha.five $+ %num.five $+ %alpha.one $+ %num.two  
  var %final.one = %pre.final $+ %pre.final.two
  while ( $len(%final.one) < %len.max ) { goto calc }  
  var %final.two = $right(%final.one,%len.max)
  var %final.three = $left(%final.one,%len.max)
  var %coin.flip = $rand(1,2)
  if ( %coin.flip == 1 ) { var %final.one = %final.two }
  if ( %coin.flip == 2 ) { var %final.one = %final.three }   
  echo -a Cut and Paste the following:
  echo -a %final.one

}

menu status {
    -
    Random Key Generator:/random.key.gen
    -
}