Some features:

The Away Button; F10:
-If you aren't away, when you press the F10 button it will set you away
-If you ARE away, it will have you return.
-You use this command if you don't have the dialog open.
-It uses the first Reason and Nick in both selective lists.
-If the above doesn't apply, as in you have not yet added a nick and/or reason, it will use "Stuff." as the default reason, and your nick with a "[a]" appended to the end.
Occurence of your nickname in chat/you're PM'd
It sends them a Private Message that you're away, for how long you've been away, and what reason.
Dialogs
The first dialog is a quicker to use than just 2 list boxes, and the 2nd dialog you can use to modify your reasons/nicks

on *:START: {
  timeridlecheck 0 1 /idlecheck
  write reasons.awy
  write nicks.awy
}
dialog a1 {
  title "Away Script"
  size -1 -1 69 49
  option dbu
  combo 1, 1 7 68 48, size drop
  combo 2, 1 24 67 50, size drop
  text "Reasons", 4, 21 0 25 7, center
  text "Nicks", 5, 21 18 25 6, center
  button "Modify", 6, 0 38 37 8
  button "Leave", 7, 39 35 30 7
  button "Return", 8, 39 42 30 7
}
on *:DIALOG:a1:sclick:6:/dialog -m a2 a2
on *:DIALOG:a1:sclick:7: {
  If (!$away) { set %returnnick $me }
  away $iif($did(1).seltext,$did(1).seltext,$iif($Read(reasons.awy,1),$Read(reasons.awy,1),Stuff.))
  nick $iif($did(2).seltext,$did(2).seltext,$iif($Read(nicks.awy,1),$Read(nicks.awy,1),$me $+ [a]))
  /amsg 4,1(15Away. Away for $iif($did(1).seltext,$did(1).seltext,$iif($Read(reasons.awy,1),$Read(reasons.awy,1),Stuff.)) 4)
}
on *:DIALOG:a1:sclick:8: {
  /amsg 4,1(15Back. Away for R:4(15 $+ $awaymsg $+ 4)15T:4(15 $+ $duration($awaytime) $+ 4))
  away
  nick %returnnick
  unset %returnnick
}
on *:DIALOG:a1:init:0: {
  If ($fopen(q)) { .fclose q }
  .fopen q reasons.awy
  While (!$ferr) && (!$feof) {
    did -a a1 1 $fread(q)
  }
  .fclose q
  If ($fopen(q)) { .fclose q }
  .fopen q nicks.awy
  While (!$ferr) && (!$feof) {
    did -a a1 2 $fread(q)
  }
  .fclose q
}
dialog a2 {
  title "Away Script"
  size -1 -1 94 79
  option dbu
  tab "Nicks", 1, 0 0 93 77
  tab "Reasons", 2
  list 3, 3 19 89 43, size
  button "Delete", 5, 3 69 29 7
  button "Clear", 6, 32 62 29 14
  button "Add", 4, 3 62 29 7
  button "Update", 7, 61 62 30 14, ok
}
on *:DIALOG:a2:sclick:7: {
  If ($dialog(a1)) {
    did -r a1 1,2
    If ($fopen(q)) { .fclose q }
    .fopen q reasons.awy
    While (!$ferr) && (!$feof) {
      did -a a1 1 $fread(q)
    }
    .fclose q
    If ($fopen(q)) { .fclose q }
    .fopen q nicks.awy
    While (!$ferr) && (!$feof) {
      did -a a1 2 $fread(q)
    }
    .fclose q    
  }
}
on *:DIALOG:a2:sclick:4: {
  set %awy $input($iif(%id = 1,Nick,Reason) to add to $iif(%id = 1,Nick,Reason) list?,evauid,Away Script,$cb(1))
  If ($len(%awy) > 0) {
    did -a a2 3 %awy
    write $iif(%id = 1,nicks,reasons) $+ .awy %awy
    If ($lines($iif(%id = 1,nicks,reasons) $+ .awy) > 0) { did -e a2 5,6 }
  }
  unset %awy
}
on *:DIALOG:a2:sclick:6: {
  set %Y/N $input(Are you sure you want to clear you $iif(%id = 1,Nick,Reason) list?,yvauwd,Away Script)
  If (%Y/N = $no) { unset %Y/N | halt }
  If (%Y/N = $yes) {
    unset %Y/N
    write -c $iif(%id = 1,nicks,reasons) $+ .awy
    did -r a2 3
    did -b a2 5,6
  }
}
on *:DIALOG:a2:sclick:5: {
  If (!$did(3).seltext) { halt }
  set %awy $iif(%id = 1,nicks,reasons) $+ .awy
  If ($fopen(q)) { .fclose q }
  .fopen q %awy
  %i = 1
  While (!$ferr) && (!$feof) {
    If ($fread(q) = $did(3).seltext) { write -dl $+ %i %awy }
    inc %i
  }
  did -d a2 3 $didwm(a2,3,$did(a2,3).seltext)
  unset %i %awy
  If ($lines($iif(%id = 1,nicks,reasons) $+ .awy) = 0) { did -b a2 5,6 }
}
on *:DIALOG:a2:sclick:1,2: {
  set %id $did
  xload
}
on *:DIALOG:a2:init:0: {
  If ($fopen(q)) { .fclose q }
  .fopen q nicks.awy
  While (!$ferr) && (!$feof) {
    did -a a2 3 $fread(q)
  }
  .fclose q
  set %id 1
  If ($lines(nicks.awy) = 0) { did -b a2 5,6 }

}
alias -l xload {
  did -r a2 3
  If ($lines($iif(%id = 1,nicks,reasons) $+ .awy) > 0) {
    If ($fopen(q)) { .fclose q }
    .fopen q $iif(%id = 1,nicks,reasons) $+ .awy
    While (!$ferr) && (!$feof) {
      did -a a2 3 $fread(q)
    }
    .fclose q
  }
  If ($lines($iif(%id = 1,nicks,reasons) $+ .awy) = 0) { did -b a2 5,6 }
  If ($lines($iif(%id = 1,nicks,reasons) $+ .awy) > 0) { did -e a2 5,6 }
}
alias f9 dialog -m a1 a1
alias f10 {
  If (!$away) {
    away $iif($read(reasons.awy,1),$read(reasons.awy,1),Stuff.)
    set %returnnick $me
    nick $iif($read(nicks.awy,1),$read(nicks.awy,1),$me $+ [a])
    /amsg 4,1(15Away. Away for $read(reasons.awy,1) 4)
  }
  If ($away) {
    /amsg 4,1(15Back. Away for R:4(15 $+ $awaymsg $+ 4)15T:4(15 $+ $duration($awaytime) $+ 4))
    away
    nick %returnnick
    unset %returnnick
  }
}
alias away {
  If (!$1) { timeridlecheck 0 1 /idlecheck }
  If ($1) { away $1- }
}
alias idlecheck {
  If ($idle >= 1500) && (!$away) {
    away Idle after 25 minutes of no action :] Cyaz!!!
    set %returnnick $me
    nick $iif($read(nicks.awy,1),$read(nicks.awy,1),$me $+ [a])
    amsg 4,1(15Away. Away for Idle after 25 minutes of no action :] Cyaz!!! 4)
  }
}
on *:TEXT:*:#: {
  If ($me isin $1-) && ($away) {
    If (!%fld. [ $+ [ $nick ] ]) { set -z %fld. [ $+ [ $nick ] ] 0 }
    If (%fld. [ $+ [ $nick ] ]) {
      If (%fld. [ $+ [ $nick ] ] < 5) { inc %fld. [ $+ [ $nick ] ] }
      If (%fld. [ $+ [ $nick ] ] >= 5) { halt }
    }
    .notice $nick 4,1(15I am currently Away. R:4(15 $+ $awaymsg $+ 4)15T:4(15 $+ $duration($awaytime) $+ 4))
  }
}
on *:OPEN:?:*: {
  If ($away) {
    If (!%fld. [ $+ [ $nick ] ]) { set -z %fld. [ $+ [ $nick ] ] 0 }
    If (%fld. [ $+ [ $nick ] ]) {
      If (%fld. [ $+ [ $nick ] ] < 5) { inc %fld. [ $+ [ $nick ] ] }
      If (%fld. [ $+ [ $nick ] ] >= 5) { halt }
    }
    .notice $nick 4,1(15I am currently Away. R:4(15 $+ $awaymsg $+ 4)15T:4(15 $+ $duration($awaytime) $+ 4))
  }
}