Ok, well I've added an edit control and a list to make it look like a combo hehehe...
Code:
On *:Start: {
  var %x = $lines(database.txt)
  while (%x) {
    ignore $gettok($read(database.txt,%x),5,32)
    dec %x
  }
}

dialog database {
  title "database"
  size -1 -1 66 116
  option dbu
  list 1, 3 14 60 80, size
  button "Add", 2, 11 96 15 8
  button "Del", 3, 38 96 15 8
  button "Close", 4, 4 106 55 8
  edit "", 5, 3 2 60 10
}

On *:Dialog:database:init:0: {
  if ($lines(database.txt) >= 1) { .play -s database.txt 10 }
}

On *:Dialog:database:sclick:2: {
  if ($did(5)) {
    if ($read(database.txt,w,did -a database 1 $did($dname,5))) { echo -a $did(5) already exists. | halt }
    did -a $dname 1 $did(5)
    write database.txt did -a database 1 $did($dname,5)
    echo -a Added $+($did($dname,5),.)
  }
}

On *:Dialog:database:sclick:3: {
  if ($did(1).sel) {
    did -d $dname 1 $did(1).sel
    write -dw $+("*,$did(1).sel,*") database.txt
    echo -a Deleted $+($did($dname,1),.)
  }
}

On *:Dialog:database:sclick:4: {
  dialog -x database database
}