function select_all() {
	var boxes = find_checkboxes();
	for (var i = 0, m = boxes.length; i < m; i++) {
		boxes[i].checked = true;
	}
}

function select_none() {
	var boxes = find_checkboxes();
	for (var i = 0, m = boxes.length; i < m; i++) {
		boxes[i].checked = false;
	}
}

function find_checkboxes() {
	var inputs = document.getElementsByTagName("input");
	var boxes = new Array();
	for (var i = 0, m = inputs.length; i < m; i++) {
		if (inputs[i].type == "checkbox") {
			boxes.push(inputs[i]);
		}
	}
	return boxes;
}