dynamic field names in a function.

I want to be able to reference NEW.field_0 though NEW.field_x where x is
coming from NEW.qty in a FOR loop of pl/pgsql function. Is this possible?

In other words:

FOR j IN 0..NEW.str LOOP

ans := ''q'' || i || ''a'' || j;
cor := ''q'' || i || ''c'' || j;
eval := 'q'' || i || ''e'' || j;

IF NEW.ans = NEW.cor
THEN NEW.eval := 1;
END IF;

END LOOP;