Not sure what you mean, Serge. Is what (exactly) necessary in order to accomplish exactly what?

Does topgear really need need to complete his class assignment? Gee, I dunno :-).
Is a VLOOKUP necessary to satisfy the assignment? Topgear says it is.
Is it necessary to change D2 to B2 in order to fix the "circular" problem? Yes, it is.
Is this exact formula the only way to do the lookup? Very doubtful; there are almost always multiple ways to do the same thing.

I note, by the way, that your code fixes a problem in topgear's formula that I missed; it checks the correct table area in the second VLOOKUP. Well done, I didn't notice it myself, so my solution, just changing D2 to B2, while necessary, would still not have done the job.