The authority of the county engineer shall be limited to the expenditure of such funds for the purpose of construction, maintenance, or repairs of public roads, bridges, ferries, or any other duties for the county as may be set aside and appropriated by the commission as hereinafter provided. It shall be the duty of the commission at some meeting in September of each calendar year, or not later than the first meeting in October following, by order or resolution spread upon the minutes, to fix and determine the amount of the funds which shall be available for the purpose of building, maintaining, and constructing public roads, bridges, and ferries of the county for the current fiscal year, beginning on October 1st, which amount, other than the salary of the county engineer and his or her necessary expenses, shall not be exceeded by him or her in building, maintaining, and constructing public roads, bridges, and ferries in the county during the period; provided, however, that the commission is authorized, from time to time within any such period, to increase the amount so allowed to be expended by the county engineer during the period, when such authorization does not conflict with the general laws of the state. Provided further, that if such funds are presently available, and have not heretofore been set aside by the present county commission, immediately on July 3, 1991, it shall be the duty of the commission to set aside a sufficient portion of the funds for the maintenance of roads, bridges, and ferries until the meeting in September or October 1991, as hereinabove provided for.