I Need Help!!!!!!!!!!!!!!!!!!!!!!

Hey people i need advice on how to convince my parents on giving me a quinceanra. You see we dont really have money to be wasting on things like that and well quite frankly im not much of a saint either so combined you know it kind of gives them a big advantage of just saying no you know. But i really really want one i mean this is a once in a life time event and i would really like to be able to have a nice memory of a quinceanera. So please please help.