if ($chr(35) !isin $active) {
    echo 4 $active Error: No are not on a channel.
  }

Use:

if ($active !ischan) {

also,

echo -a, instead of echo $active.

also:

you dont need the \"halt\" here:

  if (!$1) {
    echo 4 $active $+(4Banlist Size,$chr(32),$chr(40),$ibl($active,0),$chr(41))
    halt
  }

this is what you use:

  var %i = $1
  var %d = $ibl($active,0)
  var %o = 1
  while (%o <= %d) {
    if (%i iswm $ibl($active,%o)) {
      write wmsb.txt $+(4,[,$iif($lines(wmsb.txt) < 1, 1, $calc($lines(wmsb.txt) +1)),],) Matched string $+(,$chr(40),$1,$chr(41),) - $ibl($active,%o)
    }
    inc %o
  }
  echo 4 $+(4,$lines(wmsb.txt)) results found for string $+(%i,.)
  .play -e wmsb.txt
  .write -c wmsb.txt
}

I would use:

alias sb {
  if ($active !ischan) { echo -a Error: No are not on a channel. | return }
  if (!$1) { echo -a $+(4Banlist Size,$chr(32),$chr(40),$ibl($active,0),$chr(41)) | return }
  ; Using proper if format for the IF\'s above.
  updatenl
  ; update the ban list
  var %i = $1, %d = $ibl($active,0), %o = 1, %x, %y = $active
  ; using 1 line for all temp. vars.
  while (%o <= %d) {
    if (%i iswm $ibl($active,%o)) {
      %x = %x $v2
      var %a = $ibl(%y,%o).by, %b = $asctime($ibl(%y,%o).ctime)
      ; Set the values for the result
    }
    inc %o
  }
  echo -a $numtok(%x,32) results found for string $qt(%i)
  ; $numtok() shows how many tokens %x contains.
  if ($numtok(%x,32) != 0) echo -a %x matched %i set by %a at %b
  ; checks to $numtok is not 0.
}

Note that my code above is untested, but it should do what you want, without using the text file.

Your script resulted * /play: unable to open \'C:\Regularmirc\wmsb.txt\' (line 58, script.ini) when no matches were found. Anyhow, this script above you be fine. No color codes though ;p