function Kalender(veld)
	{
	window.open('kalender.php?veld=' + veld, 'Kalender', 'width=200, height=300, scrollbars=yes, menubar=no, directories=no, resizable=no');
	}

function select_datum(datum, veld)
	{
	opener.document.frm_website.elements[veld].value = datum;
	
	window.close();
	return true;
	}