I've been pumping since DD was born, we had latch issues, and I had three lactation consultants helping me to no avail

It's been going great, and I did have a small "store" of frozen breast milk for a while, but we've gone through that already.
Well, I have to go out of town all day Saturday, so I've been trying to pump more for the last week. Apparently she's hitting a growth spurt or something, because as soon as I get a bag or two in the freezer, she's needing to be fed and I don't have any fresh ready for her. She's not super heavy anyway, I don't want to try and "trick" her into not eating or something - she's in about the 25th percentile for weight, and I'd like to keep her gaining (I never did well weight wise, and like me, she is on tops for height - tall and lean I guess).
I have some bottles of ready mixed Good Start from when we were supplementing from the hospital, and we tried that last night. NO GO. Man, did she give us the nastiest look and spit the bottle out! We gave her some breastmilk, and she took that, then we tried the formula again, and that time she gave us the nasty look and started to cry. Back to breast milk.
Today, I found some Similac powder samples, individual packs, and made one up. Same deal. She'll suck on the bottle, happy as a can be for a second, then look like she sucked on a lemon, and spit everything in her mouth out and use her tongue to push the bottle out.
I have a call into our doctor to see if he has any tips or ideas. I just need to get DH through that day with her. I'm going to have to be away for this thing probably 2 or 3 more times over the next month or so - not doing it is not an option, as it's a HUGE commission deal (I'm selling some horses for someone, and the commission will have us well set into the winter).
Help?