For the purpose of making grants to States under part B of this subchapter to assist States in meeting the costs of vocational rehabilitation services provided in accordance with State plans under section
721 of this title, there are authorized to be appropriated such sums as may be necessary for fiscal years 1999 through 2003, except that the amount to be appropriated for a fiscal year shall not be less than the amount of the appropriation under this paragraph for the immediately preceding fiscal year, increased by the percentage change in the Consumer Price Index determined under subsection (c) of this section for the immediately preceding fiscal year.