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;