After the adoption of the annual appropriation ordinance, no further appropriations may be made at any other time during that fiscal year, except the board may amend its appropriation ordinance from time to time by the same procedure required by this Act for the original adoption of the appropriation ordinance. Transfer from one appropriation of any one fund to another of the same fund, not affecting the total amount appropriated, may be made at any meeting of the board by a two-thirds vote of all the members constituting the board. By a like vote the board may make appropriations in excess of these authorized by the appropriation ordinance in order to meet an immediate emergency.
70 ILCS 1105/21