=INDEX(C1:C100,MATCH("USA"&"AUTOMOBILE",A1:A100&B1:B100,0))
which is an array formula, it should be committed with Ctrl-Shift-Enter, not
just Enter.
Excel will automatically enclose the formula in braces (curly brackets), do
not try to do this manually.
When editing the formula, it must again be array-entered.
--
HTH
Bob
(there's no email, no snail mail, but somewhere should be gmail in my addy)