Error percentage calculated in excel and matlab not matching. why?

I calculated error percentage for actual and predicted after ANN implementation using below code. Same I calculted using excel. both are not matching . why?

x = input';

t = output';

trainFcn = 'trainlm'; % Levenberg-Marquardt backpropagation.

hiddenLayerSize = 30;

net = fitnet(hiddenLayerSize,trainFcn);

net.divideParam.trainRatio = 80/100;

net.divideParam.valRatio = 10/100;

net.divideParam.testRatio = 10/100;

[net,tr] = train(net,x,t);

y = net(x);

e = gsubtract(t,y);

percentage_error = abs(t- y) / abs(t) * 100;

[Cris LaPierre]

Without the data, it is impossible for us to say. Save your variables to file and attach that to your post using the paperclip icon.