Neural Prediction Control for MIMO systens

Hi, I've been trying to use the NN Predictive Control of the Neural Network Toolbox to control a MIMO system, however it appears that it doesn't accept this kind of systems, but just SISO. am I doing something wrong or there's another way of doing that?

My system is a 2 imput 2 output one, and I keep getting this error when trying to identify it using the NN Predictive Control Block on simulink.

    ??? Error using ==> nnident at 1574
    Invalid external input specified. The input
    has 1 data columns while the sum of the port
    widths of all inports in the model is 2.

    Error in ==> nncontrolutil at 20
    feval(command,varargin{:});

All the best Jhonatam