Something

menu * {
  Away script:/dialog -m away away
}
dialog away {
  title "Away system made by `ferdi"
  size -1 -1 217 68
  option dbu
  button "Away", 1, 7 50 37 12
  button "Back", 2, 173 50 37 12
  button "Exit", 3, 90 50 37 12, cancel
  edit "Add away reason here", 4, 7 14 206 12
  text "Away reason:", 5, 90 4 87 8
}
On *:dialog:away:sclick:1: {
  /amsg [Away-system] I'm now away! Reason: $did(4) left at: $time
  set %away $ctime
}
on *:dialog:away:sclick:2: {
  /amsg i'm now back from $did(4) I was away for: $+ $duration($calc( $ctime - %away ))
/unset %away
}