I'm practicing programming at the moment and I don't see why it wouldn't be possible... but since I'm still a newbie I'm sure Joe or one of the other programmers would know better than I do.
EDIT: Just tried it out, seems there is two requests with one being the Negg ID (don't know the ID's) and one that let's you know the worth of the exchange. I'll try creating a simple test to see if it works.
EDIT 2: So it seems that buying the Neggs is easy... the part that I don't know is each Negg seems to have it's own separate ID and I'm not sure of them... so unless you have every single Negg lying around web scraping will have to do.