var vorigezone;
function toonzone(hzone)
{	
	var i = hzone.replace("zone",""); 
	var hzonediv = document.getElementById(hzone);
	document.form.objselect.options[i].selected  = true;
	if (hzonediv)
	{ 	
		if (vorigezone != hzonediv) 
		{
			document.getElementById('vorigezone').style.visibility = 'hidden';
		} 
		hzonediv.style.visibility  = 'visible';
		vorigezone = hzonediv;
	}
	return true;
}
   
function verbergZone(zone)
{	
	var vzone = document.getElementById(zone);	
	if (vzone)
		vzone.style.visibility='hidden';
	return true;
}// JavaScript Document