Mommies on gvg, question is I'm going out for a party, I have 240ml of…

Mommies on gvg, question is I'm going out for a party, I have 240ml of milk, but now it's not enough for the baby And I'm pumping for 40 minutes 30ml ? very little and long I barely managed 240 in three days, froze all So I'm thinking, who tried this, there won't be enough milk naturally, give the mixture once or twice while I'm gone? I think giving it once shouldn't cause any problems