You could easily use a cell array:
N = 100;
Z = cell(1,N);
for k = 1:N
... your code
Z{k} = whatever you want to store
end
The stored data from each iteration is available in Z.
After the loop you can likely concatenate the contents of the cell array using
A = cat(1,Z{:}) % Or 2, depending on the array sizes.
