Try this:
fold_list = cellstr(strcat('Folder_',num2str((100:125).','%#4.d')));
% By the way: Simpler:
% fold_list = sprintfc('folder_%03d', (100:125).'):
user_lists = cellstr(strcat('User_',num2str((1:100).','%#6.d')));
base_url = 'https://mydomain.com';
n_folds = length(fold_list);
n_users = length(user_lists);
checklist = cell(n_users+1,n_folds+1);
checklist(2:end,1) = user_lists;
checklist(1,2:end) = fold_list;
C = cell(n_users,n_folds)
parfor j=1:n_users
for k=1:n_folds
try
C{j,k} = webread([base_url '/' fold_list{k} '/' user_lists{j} '.txt']);
catch
C{j,k} = 'N/A';
end
end
end
cecklist(2:end, 2:end) = C;
