SQL> ed
Wrote file afiedt.buf

  1  declare
  2   v_name varchar2(30);
  3   v_sum number;
  4   procedure p(p_ncol number) is
  5   begin
  6    --ваша MONITORING_SALES
  7    select column_name into v_name from user_tab_columns where table_name='EMP' and COLUMN_ID=p_ncol;
  8    --emp ваша
  9    execute immediate 'select sum('||v_name||') from emp' into v_sum;
 10    dbms_output.put_line('Сума по колонке '||v_name||' = '||v_sum);
 11    dbms_output.put_line('');
 12   end;
 13  begin
 14   p(6);
 15   p(7);
 16* end;
SQL> /
Сума по колонке SAL = 29025
Сума по колонке COMM = 2200

PL/SQL procedure successfully completed.