Science Buddies: "Ask an Expert"

Hi. As part of my science fair project I used DCPIP to try and work out the concentration of Vit C in store brought juices. We only had a small amount of DCPIP so pipetted small volumes of OJ into 1 ml volumes of DCPIP. Problem is all the literature works out mg of Vit C by titrating DCPIP into OJ and not the other way round. I didn’t do a standard curve, I just added the OJ to the DCPIP and now I can’t figure out how to work out the mg of Vit C in the OJ. Help please.