function comboAdd(combo, text, wert) {
  var neu;
  neu = new Option(text, wert);
  combo.options[combo.length] = neu;
}

function comboClear(combo) {
  var i;
  for (i = combo.length - 1; i >= 0; i--)
    combo.options[i] = null;
}

function val(c) {
  if (c.length == 0)
    return 0;
  else
    return Number(c);
}