function vaart(){
         var a = document.getElementById('maxton');
         var b = document.getElementById('aanton');
         var c = document.getElementById('aanprijs');
         var d = document.getElementById('dagen');
         var e = document.getElementById('opbr');
         var maxton = parseFloat(a.value);
         var aanton = parseFloat(b.value);
         var aanprijs = parseFloat(c.value);
         var dagen = parseFloat(d.value);
		
         e.value = (aanprijs*aanton)/maxton/dagen;
}     
	  
 function formatNumber()
{
var obj = document.getElementById('opbr');
var num = new NumberFormat();
num.setInputDecimal('.');
num.setNumber(obj.value); // obj.value is '0,676923076923077'
num.setPlaces('2', false);
num.setCurrencyValue('€ ');
num.setCurrency(true);
num.setCurrencyPosition(num.LEFT_OUTSIDE);
num.setNegativeFormat(num.LEFT_DASH);
num.setNegativeRed(false);
num.setSeparators(true, ',', ',');
obj.value = num.toFormatted();
}