function calcul() {
	var total = 0;
	var ht = 0;
	var tva = 0;
	var nb;
	nb = document.devis.coche.length;
	total = eval(document.devis.prix_base.value);
	for( i = 0 ; i < nb ; i++ ) {
		if (document.devis.coche[i].checked) total = total + eval(document.devis.coche[i].value);
		}
	document.devis.prix_total.value = total;
	ht = Math.round(((total / 119.6)*100)*100)/100;
	document.devis.ht.value = ht;
	tva = Math.round(((19.6*ht/100)*100))/100;
	document.devis.tva.value = tva;
	}