getElementsByName()

Object.prototype.getElementsByName2 = function (name) {
	var elements = document.getElementsByName(name);
	var resultat = new Array();
	
	for (i=0; i<elements.length; i++) {
		if (elements[i].isChildOf(this)) {
			resultat.push(elements[i]);
		}
	}
	
	return resultat;
}

Object.prototype.isChildOf = function (parent) {
	var child = this;
	while (typeof (child = child.parentNode) != "undefined" && child != null) {
		if (child == parent) {
			return true;
		}
	}
	return false;
}

var list = document.getElementById(id).getElementsByName2(name);
	
for (i=0; i<list.length; i++) {
	// Pour chaque élément trouvé
}