The Secretary shall establish and maintain a program to attract Indian professionals who are graduates of a course of postsecondary or graduate education for employment in either the Bureau agriculture or related programs or, subject to the approval of the tribe, in tribal agriculture or related programs. According to such regulations as the Secretary may prescribe, such program shall provide for the employment of Indian professionals in exchange for the assumption by the Secretary of the outstanding student loans of the employee. The period of employment shall be determined by the amount of the loan that is assumed.