The Neural Network Toolbox is optimum for training a neural network.
Whenever possible, use MATLAB command line syntax to first train your neural network. Once you have trained your neural network, you can use the GENSIM command from the Neural Network Toolbox to export the network to Simulink and simulate it. More information on the GENSIM function can be found at the following URL:
Another option would be to write a MATLAB file S-Function that will train your network adaptively. For general information on S-functions, visit the following URL:
Finally, the following URL shows a user-contributed file "nnsysid.zip" that demonstrates how you can use Simulink blocks to implement Neural Network algorithms:
Note that the MathWorks does not guarantee or warrant the use or content of user contributed submissions like the one above. Any questions, or issues should be directed to the contributing author.