function updateMainRegion() {
  var countrySelect = document.forms.Unterkunftsdaten.land;
  var mainRegionSelect = document.forms.Unterkunftsdaten.hauptregion;
  mainRegionSelect.options.length = 0; // DropDown Menü entleeren
  mainRegionSelect.style.visibility="hidden";
  if (countrySelect.options[countrySelect.selectedIndex].value=="D") {
    mainRegionSelect.style.visibility="visible";
    var mainRegionName=new Array ("","Baden-Württemberg","Bayern","Berlin","Brandenburg","Bremen","Hamburg","Hessen","Mecklenburg-Vorpommern","Niedersachsen","Nordrhein-Westfalen","Rheinland-Pfalz","Saarland","Sachsen","Sachsen-Anhalt","Schleswig-Holstein","Thüringen");
    var mainRegionWert=new Array ("","D_BW","D_BY","D_BE","D_BG","D_BR","D_HH","D_HE","D_MV","D_NI","D_NO","D_RP","D_SL","D_SN","D_SA","D_SH","D_TH");
  }    
    
  if (countrySelect.options[countrySelect.selectedIndex].value=="A") {
    mainRegionSelect.style.visibility="visible";
    var mainRegionName=new Array ("","Burgenland","Kärnten","Niederösterreich","Oberösterreich","Salzburg","Steiermark","Tirol","Vorarlberg","Wien");
    var mainRegionWert=new Array ("","A_BL","A_KT","A_NI","A_OB","A_SA","A_ST","A_TI","A_VO","A_WI");
  }    
   	
  for(var i in mainRegionName) {
    mainRegionSelect.options[i] = new Option(mainRegionName[i], mainRegionWert[i]);
  }
}