// context = id of elements which contains checkboxes
// controller = DOMelement of ckeckbox controller
function checkall(context, controller){
	$("#"+context).find("input[@type$='checkbox']").not(controller).each(function(){
		// verify the state of checkbox controller and pass the state to others checkboxes
                this.checked = $(controller).checked;
	});
}

Select all checkbox in the specific context.
Need jQuery Framework : http://jquery.com/

[ jQuery ] Checkbox Controller

jquery

JavaScript