The members of the commission shall receive a per diem, mileage and expenses as is authorized by law per day for each day spent in attending meetings of the commission and in performing such other duties as may be required of them by law or the directives of the commission. However, except for regular or called meetings no member shall receive per diem, mileage or other expenses in performing duties unless such duties shall have been directed by an order duly entered on the minutes of a meeting of the commission prior to the performance thereof.