numbers but allow "-" or "/" or "(" characters?
Code:
function validateNumber(field, msg, min, max) {
	if (!min) { min = 0 }
	if (!max) { max = 255 }

	if ( (parseInt(field.value) != field.value) ||
             field.value.length < min ||
             field.value.length > max) {
		alert(msg);
		field.focus();
		field.select();
		return false;
	}

	return true;
}
Thanks!