Breast feeding. Help!!!


Hello so I am exclusively breast feeding, I am using the manual breast pump but can’t get any milk out, I have a 15 to attend tonight, I am the quinceañeras God mom but I’m not pumping enough. I’m leaving my 2 week year old with my mom because the 15 is will be outside. But if I’m not pumping enough what can I do? Supplement formula just for tonight?! Please help any advice TYIA!