Simulate the Neural network ?

Hi , i am testing my modular neural network so First what's the difference between sim and train ? 2-when i call the sim function the matlab error ('model' parameter must be a string ) appears .It seems confused with the simulink toolbox. I store the neural network in an array cell so this is the code : for i=1:size(trainInput,1) %find cluster for the ith training input cn=m2(i); % find output by respective module nets{cn} is a neural network responsible %of a part of the data . module=nets{cn}; a = sim(module,trainInput(i,:)'); a=a'; % corr is counter for correcte predicted class if a(1)<0.5 rep=0; else rep=1; end; if trainOutput(i)==rep corr=corr+1; end; end; I hope somebody can help me :)