function ClearForm3()
{
  document.form3.manufacturer.value = "I";
  document.form3.model.value = "";
  document.form3.mn.value = "I";
  document.form3.mx.value = "I";
  document.form3.zip.value = "I";
}


function checkForm(){
  var brandString = document.form3.manufacturer[document.form3.manufacturer.selectedIndex].value;
  var selectedItemFrom = document.form3.yearfrom.options[document.form3.yearfrom.selectedIndex].value;
  var selectedItemTo = document.form3.yearto.options[document.form3.yearto.selectedIndex].value;
  if (brandString == "I") {
    alert("Kies eerst een merk");
    return false;
  }
  if (selectedItemFrom > selectedItemTo) {
    alert("Bouwjaar (min) moet een lager jaartal zijn dan bouwjaar(max)!");
    return false;
  }
  frm.submit();
  return false;
}