Cell References in LOOKUP Function

Greetings,

I could really use some help. I've been using the LOOKUP function to pull data from another sheet that contains a large amount of structured data produced by another application. See G1 in the attached example. The problem is that the lookup vector and result vector change often, and there are hundreds of these lookup vectors. I'm able to identify these vectors (columns A-D in the example), but I can't seem to figure out how to work them into the LOOKUP formula. I've played with INDIRECT and tried to use OFFSET but I must be doing something wrong.

Thanks,