var allchecked = false;
function set_all_array(formname, fieldname, button){
    allchecked = !allchecked;

    for(i=0; i < document.forms[formname].elements[fieldname + "[]"].length; i++){
	document.forms[formname].elements[fieldname + "[]"][i].checked = allchecked;
    }
    document.getElementById(button).value = (allchecked? "Uncheck All" : "Check All");
}