function selectPackage(number) {
	var packages = document.selectmembership.form_package;
	if (isArray(packages)) {
		packages[number].checked = 'checked';
	} else {
		packages.checked = 'checked';
	}
}

function isArray(obj) {
	try {
		obj[0].checked;
		return true;
	} catch (err) {
		return false;
	}
}