Until July 1, 1998, an active participant in this System who has at least 6 years of service as a judge may establish up to 2 years of service credit in this System for a period during which the participant held elective office as a member of a board of education in this State or a member of the board of trustees of a community college district in this State, by applying to the Board in writing and paying to the System an amount equal to (1) employee contributions based on the rate in effect for a judge on the date of becoming a participant in this System and the salary received by the judge on that date, plus (2) the employer’s share of the normal cost of the benefits being established, plus (3) interest thereon at the prescribed rate, compounded annually, from the date of membership to the date of payment. However, credit may not be established under this Section for any period for which the judge has received credit under any other pension fund or retirement system subject to this Code, unless that credit has been terminated.