source: ResearchApps/PHY/MIMO_OFDM/bbReplace.m

%Script assumes the OFDM PHY model is open and is the current model

subsys = '/OFDM Rx MIMO/Equalizer & Packetizer/Packet_Constructor';
fec_dec = find_system([bdroot subsys],  'block_type', 'blackbox2');
fec_dec_h = get_param(fec_dec, 'Handle'); fec_dec_h = fec_dec_h{1};
orig_pos = get(fec_dec_h, 'Position');
orig_init = get(fec_dec_h, 'init_code');
orig_sim = get(fec_dec_h, 'sim_method');

oldind = str2double(fec_dec{1}(end));

%Adding then deleting will "fix" the problem
fec_dec_new_h = add_block('xbsIndex_r4/Black Box', [bdroot subsys '/fec_decoder ' num2str(oldind+1)], 'init_code', orig_init);
set(fec_dec_new_h, 'sim_method', orig_sim');
delete_block(fec_dec_h);

%Deleting then adding will *not* fix it
%delete_block(fec_dec_h);
%fec_dec_new_h = add_block('xbsIndex_r4/Black Box', [bdroot subsys '/fec_decoder 2'], 'init_code', orig_init);
%set(fec_dec_new_h, 'sim_method', orig_sim');

%Place the new block where the old one was, auto-connecting all ports
set(fec_dec_new_h, 'position',  orig_pos);

save_system