I would do something along the lines of:
Randomize = randperm(length(input));
inputRandom = input(Randomize);
outputRandom = output(Randomize);
for i=1:10
Xtest = inputRandom(((i-1)*10+1):i*10);
ytest = outputRandom(((i-1)*10+1):i*10);
Xtrain = inputRandom; Xtrain(((i-1)*10+1):i*10) = [];
ytrain = outputRandom; ytrain(((i-1)*10+1):i*10) = [];
[b,bint,r,rint,stats] = regress(ytrain,Xtrain);
YCrossValidated = Xtest*b;
crossValidateResiduals = YCrossValidated - Ytest;
% Calculate any fit statistics HERE and STORE anything you need.
end
