I am not how to make simulink warn you but perhaps you could try writing a short script that will automatically connect the blocks for you in order (assuming their port names remain the same). You would use the add_line command: Add Line You could create a dummy subsystem that you would place in the system with your A,B,C and D blocks and when double clicked it could run the script to automatically connect all the blocks in the proper order. You would do this by making a mask on the subsystem and using the callbacks to run the script.
Hope this helps!
