function confirm_validate()
{
	elements = document.forms[0].elements;
	var fields = "";
	for (i = 0; i < elements.length; i++) {
		if ((elements[i].value == "") && ((elements[i].name == "achternaam")||(elements[i].name == "telefoon")||(elements[i].name == "email"))) {
			var name="";
			switch (elements[i].name) {
				case "achternaam":
					name = "Achternaam";
				case "telefoon":
					name = "Telefoonnummer";
					break;
    			case "email":
       				 name = "E-mailadres";
        			break;
			}
			fields = fields + "\t" + name + "\n";
		}
	}
	if (fields != "") {
		alert('U bent vergeten de volgende velden in te vullen :\n\n'+fields);
		return false;
	}
	else {
		var msg=confirm("Weet u zeker dat het formulier verstuurd moet worden?");
		if (msg) {
			return true ;
		}
		else {
			return false ;
		}
	}
}