I notice that you are using R2016a, so I will not mention some of the possibilities for later releases
You cannot do that with a numeric array.
If you convert it to a cell array of numbers, and leave some entries empty, then you can cell2table() and writetable()
You can use dlmwrite() with append set, to write one line of values at a time.
You can experiment with putting in nan for the entries that you want to be blank, and convert to table, and use writetable(). At some point, nan started being writen out as empty, but I am not sure how early that was.
If this is for uitable for display purposes, then you can create a cell array of character vectors, leaving some of the cells empty, and setting the uitable Data property to the cell. If you do this, then if you permit editing the user will be able to enter text instead of numeric; you will need to str2double() and check for nan if you accept input on the uitable.
You will not be able to do what you want with the Variable Brower.