A New mathematical analysis is presented for efficient computation of BER of Multicode Multicarrier Direct Sequence CDMA System in presence of Multipath Rayleigh Fading. A New explicit expression is derived for optimizing BER of a Multicarrier system model that accounts for both Intra band and Cross band ISI. The proposed BER Optimization algorithm resides entirely at the receiver so that the distortion experienced by each active user is significantly reduced. The numerical results have shown that optimizing BER is capable of selecting a carrier with suitable frequency that enhances the performance at the decoding section of Multicode Multicarrier Direct Sequence CDMA System. Further, simulation results corroborate the effectiveness of BER optimization algorithm in improving the performance under typical demanding Multiple Access conditions.