// function to calculate the total prijs field
function Total() {
   var tot = 0;
   tot += (10 * document.endles.artikel1.value);
   tot += (10 * document.endles.artikel2.value);
   tot += (15.5 * document.endles.artikel3.value);
   document.endles.totaalprijs.value = tot;
}
// function to update prijs when quantity is changed
function UpdatePrijs(number, unitprijs) {
   prijsname = "prijs" + number;
   artikelname = "artikel" + number;
   var a = document.endles[artikelname].value;
   document.endles[prijsname].value = a * unitprijs;
   Total();
}
//global variable for error flag
var errfound = false;
//function to validate by length
function ValidLength(item, len) {
   return (item.length >= len);
}