Write a string of alphanumeric letters to an Excel spreadsheet

I am trying to write a string of alphanumeric letters to an Excel spreadsheet. This is what I have so far:

exl = actxserver('excel.application');
exlWkbk = exl.Workbooks;
exlFile = exlWkbk.Open(['C:\path\exlfile.xlsm']);
exlSheet1 = exlFile.Sheets.Item('Sheet1');
exl.visible = true;
for k=1:4
        for i=1:4
            n=n+1;
            exlSheet1.Range(['B' num2str(n)]).string = Affinity(i,j,k);
        end
    end
end
exlWkbk.Close;
exl.Quit;