I think there were a few posts on expressing and stuff about a week ago. but it definately can be done. You will find that if you want to give formula once a day it would be best to do it at the same time as you will effectively be dropping a breastfeed. I did this with Ayja and it was fine.
Anyway if you have a look in the measuring breastmilk post that ANdie started I think there should be a heap of stuff in there about giving bottles and breastfeeding and expressing.
Good luck and good to hear from you.