iPhone：在联系人中创建自定义字段

i am developing a application in which i add contact to contact List. i am able to basic info like name, address, email, phone, notes etc. but i want to add some custom field like userLabel1, userValue1 , bioPersonal, bioWork, bioOther. so i want to add custom fields to address Book'contacts.i am developing a application in which i add co