function calculQ (F) {
  var Q = F ; 
  var PU = F.form.elements[F.name.replace("q_","pu_")];
  var PT = F.form.elements[F.name.replace("q_","amount_")];
  var quantite = Q.value;
  var prix = parseFloat(PU.value);
  var total = prix*quantite ;
  PT.value = total ;
  calculTotal(F.form) ;
  	
   var item_name = F.form.elements["item_name"] ;
   var reg=new RegExp(F.name.replace("q_","")+":\d/g");
   var change = F.name.replace("q_","")+":"+quantite+" " ;
   //TODO le remplacement en parche pas...
   if (item_name.value.search(reg)!=-1) {
	alert('existe déj');
	item_name.value.replace(reg,change); 
   }
   else {
   	item_name.value += " " +change ; 
   }
}

function calculTotal(F) {
  var elems=new Array();
  var somme=0;
  for (var i=0;i<F.elements.length;i++) {
    if (F.elements[i].name.indexOf("amount_")!=-1) elems.push(F.elements[i]);
  }
  for (var i=0;i<elems.length;i++) {
    somme+=parseFloat(elems[i].value);
  }
  F.elements["totalamount"].value = somme;
  F.elements["amount"].value = somme;
}