if (window.Event) 
	document.captureEvents(Event.MOUSEUP); 
	function nocontextmenu() 
		{ 
		event.cancelBubble = true 
		event.returnValue = false; 
		return false; 
		}	 
	function norightclick(e) 
		{ 
		if (window.Event) 
			{ 
			if (e.which == 2 || e.which == 3) 
				return false; 
			} 
		else 
			if (event.button == 2 || event.button == 3) 
				{	 
				event.cancelBubble = true 
				event.returnValue = false; 
				return false; 
				} 
			} 
	if (document.layers) 
		{ 
		document.captureEvents(Event.MOUSEDOWN); 
		} 
	document.oncontextmenu = nocontextmenu; 
	document.onmousedown = norightclick; 
	document.onmouseup = norightclick; 


// controle selectveld
function getSelectedButton(buttonGroup)
	{
	i=0;
	for (var i=0;i<buttonGroup.length;i++)
		{
		if (buttonGroup[i].checked)
			{
			return i
   			}
  		}
  	return -1;
	}

// controle positief getal
function isPosInteger(getal)
	{
	invoer=getal.toString()
	for (var i=0; i<invoer.length; i++)
		{
		var teken = invoer.charAt(i);
		if(teken < '0' || teken > '9')
		return true;
		}
	return false;
	}

// controle leeg veld
function IsEmpty(input)
	{
	if (input==null || input=="")
		{
		return true
		}
	return false
	}

function changeImages() 
	{
	for (var i=0; i<changeImages.arguments.length; i+=2) 
		{
		document[changeImages.arguments[i]].src = changeImages.arguments[i+1];
		}
	}