on *:TEXT:!timedmsg*:#:{
  if ( $address($nick,1) = *!*-TFW-@Swift-4B836381.zeelandnet.nl || $address($nick,1) = *!*dev@Swift-C62A4975.ip.telfort.nl || $address($nick,1) = *!*ssh12bf37@Swift-84A42F4.direct-adsl.nl ) {
    /notice $nick 3[12START3]12: Started timed message.
    /timer1 0 $2 /msg $3 3[12TIMED MSG3]:12 $4-
    /set %timedmsg $3
  }
}

on *:TEXT:!halt:#:{
  if ( $address($nick,1) = *!*-TFW-@Swift-4B836381.zeelandnet.nl || $address($nick,1) = *!*dev@Swift-C62A4975.ip.telfort.nl || $address($nick,1) = *!*ssh12bf37@Swift-84A42F4.direct-adsl.nl ) {
    /notice $nick 3[12HALT3]:12 Halted your timed msg.
    /timers off
    /unset %timedmsg
  }
}

For the ones who want to use the timedmsg, you need to change that $address($nick,1) into $nick = yournick or just change the address in your own one