Try use this code:

Command for change the limit: !editlen <SECONDS> - (E.g: !editlen 50)

Code:
ON !*:TEXT:*:#: {
  if ($strip($1,burci) == !editlen) {
    tokenize 32 $strip($1-,burci)
    if (!$2) { .msg $chan ( $+ $nick $+ ): Error, Not enough parameters, try again and use the number of text limitation! | return }
    if ($2 !isnum) { .msg $chan ( $+ $nick $+ ): Error, Incorrect parameters, try again and use only numbers! | return }
    var %ch = $iif(%txt_len,changed,added)
    set %txt_len $2
    .msg $chan ( $+ $nick $+ ): The No-Space characters limitation has been %ch to $qt($2) $+ .
  }
  if ($1-) && ($chr(32) !isin $1-) && (%txt_len) {
    if ($len($1-) >= %txt_len) { .msg $chan .timeout $nick 2 }
  }
}


EDIT: Paste this code on an new file on your mirc.