You can save a file in a format compatible with older versions of Microsoft Excel by using the SAVEAS method of Workbooks and specifying an input argument as in the example below:
file = 'C:\myfilename.xls';
xlswrite(file, rand(5));
myApp = actxserver('Excel.Application');
myApp.visible = 1;
workbook = myApp.Workbooks.Open(file);
workbook.SaveAs('C:\myfilename2.xls',43);
%Saves the file in a format compatible with MS Excel 95 and 97
myApp.Quit;
