function MM_validateForm() { //v4.0
  if (document.getElementById){
    var i,p,q,nm,test,num,min,max,errors='',args=MM_validateForm.arguments;
    for (i=0; i<(args.length-2); i+=3) { test=args[i+2]; val=document.getElementById(args[i]);
      if (val) { nm=val.name; if ((val=val.value)!="") {
        if (test.indexOf('isEmail')!=-1) { p=val.indexOf('@');
          if (p<1 || p==(val.length-1)) errors+='- '+nm+' must contain an e-mail address.\n';
        } else if (test!='R') { num = parseFloat(val);
          if (isNaN(val)) errors+='- '+nm+' moet een nummer bevatten.\n';
          if (test.indexOf('inRange') != -1) { p=test.indexOf(':');
            min=test.substring(8,p); max=test.substring(p+1);
            if (num<min || max<num) errors+='- '+nm+' must contain a number between '+min+' and '+max+'.\n';
      } } } else if (test.charAt(0) == 'R') errors += '- '+nm+' is een verplicht invulveld.\n'; }
    } if (errors) alert('Er waren probleem met het formulier:\n'+errors);
    document.MM_returnValue = (errors == '');
} }
//-->

function updateFormPrice(offset) {
	var price 			= document.getElementById('price['+offset+']').value;
	var amount 			= document.getElementById('option['+offset+']').value;
	var total_price = price*amount;
	var nr_options 	= 9;

	// update het veld van de huidige row	
	document.getElementById('total['+offset+']').value=total_price;
	
	// update het totaalveld
	var total_value = 0;
	for (var i=0; i<nr_options; i++) {
		total_value = total_value + parseFloat(document.getElementById('total['+i+']').value);
	}
	document.getElementById('totaalbedrag').value=total_value;
	
	return true;
}