I have no doubt English like syntax is a terrible idea but this seems like a surprisingly readable example.
sales_tax_amount = balance * state[42].tax_rate;
(Assuming I've guessed the meaning of the Cobol correctly - perhaps that's the rub.)(ETA: Added semicolon.)
(ETA2: Fixed critical indexing bug.)
Note the semicolon is significant. Barbaric, I know.
So that'd be state[42].
I've put in a PR to upstream. LGTM
#define MULTIPLY sales_tax_amount = balance * state[43].tax_rate; //