Code:
dialog test {
  title "mIRC"
  size -1 -1 110 100
  option dbu
  list 1, 15 34 80 48
  edit "", 2, 15 22 80 10, autohs
  button  "Rem", 5, 40 82 30 10
}

on *:dialog:test:init:*: {
  ;Add some words
  did -a $dname 1 Some
  did -a $dname 1 Other
  did -a $dname 1 Help
  did -a $dname 1 Word
}
on *:dialog:test:sclick:*: {
  ;case 1 - Button: remove a selected word in the listbox - select word AND press Rem
  if ($did == 5) {
    did -d $dname 1 $did($dname,1).sel
  }
}
on *:dialog:test:edit:*: {
  ;case 2 - Edit : type some word in the edit, some word that exists in the ListBox
  if ($did == 2) {
    if $_found($dname,1,$did($did)) {
      did -c $dname 1 $ifmatch
      did -d $dname 1 $did($dname,1).sel
      did -r $dname 2
    }
  }
}

alias _found {
  var %f = $did($1,$2).lines
  while (%f >= 1) {
    if ($gettok($did($1,$2,%f),1,32) == $3) return %f
    dec %f 
  }
  else return 0
}


Case 1 - Button , Case 2 - Edit
One last effort :P