Pumped milk freezing question

F

I bought a little hand pump while I was pregnant for the odd occasion that hubby and I want to go out without baby and such an occasion is coming up this Saturday night. I'm pumping small amounts after each feed (I can usually get about 40ml/1.5oz) and am freezing it. I just want to know if it'll be okay for me to just add the freshly pumped milk to the milk I've already pumped and frozen? Or if I can't, how should I be doing it?