var dyn_carsOptionTree = [['7',[['A3','42'],['A4','43'],['A6','45']]],['10',[['3 Series','86'],['5 Series','87'],['X5','98']]],['26',[['Fiesta','252']]],['53',[['E Class','448'],['Sprinter','883']]],['78',[['Leon','673']]],['92',[['Insignia','1444']]],['93',[['Golf','812']]]]
function populateTarget(name,triggerObj,targetObj,emptyText) {

  eval ('tree = ' + name + 'OptionTree')

  triggerValue = getValue(triggerObj)

  for (i=0;i<tree.length;i++) {

    if (tree[i][0]==triggerValue) {
      break
    }

  }

  empty(targetObj)

  newOption = new Option()
  newOption.text = emptyText;

  newOption.value = ""
  targetObj.options[targetObj.options.length] = newOption

  if (i<tree.length) {

    options = tree[i][1]
    selectThisOption = 0

    for (i=0;i<options.length;i++) {

      newOption = new Option()
      newOption.text = options[i][0]
      newOption.value = options[i][1]
      targetObj.options[targetObj.options.length] = newOption

    }

    targetObj.options.length = options.length + 1;
  }

}

function empty(select) {

  select.options.length = 0

}

function getValue(formObj) {

  value = null

  if (formObj.options) { // select

    if (formObj.selectedIndex > -1)
      value = formObj.options[formObj.selectedIndex].value

  } else {

    if (formObj.length) { // radio
      for (var b = 0; b < formObj.length; b++)
        if (formObj[b].checked)
          value = formObj[b].value
    }
    else if (formObj.checked) // checkbox
      value = formObj.value

  }

  return value

}