function showSelectedSubBox(select) {
  var wert = select.options[select.options.selectedIndex].value;
  hideContactElements();
  showContactElement(wert);
}

function showContactElement(elementID) {
  elementToChange = document.getElementById(elementID);
  if (elementToChange.style.display=='none') {
    elementToChange.style.display='block';
  } else {
    elementToChange.style.display='none';
  }
}

function hideElement(elementID) {
  elementToChange = document.getElementById(elementID);
  if(elementToChange != null) {
    elementToChange.style.display='none';
  }
}

function hideContactElements() {
  hideElement("defaultDetails");
  hideElement("bookingDetails");
  hideElement("proposalDetails");
}