Export to excel from macbook

I want to export my data to 2 CSV (or Excel) spreadsheets into one file, but different sheets. I've tried using xlswrite(filename,A,sheet,xlRange), but found out that does not work on MacBook or Ubuntu/Linux (the only computers I'm using this for). I tried XLWrite function http://www.mathworks.com/matlabcentral/fileexchange/38591-xlwrite--generate-xls-x--files-without-excel-on-mac-linux-win which works for exporting to an .XLS file, but I cannot do multiple sheets with it. Any advice??

[Geoff Hayes]

Alexandra - the comments for the xlwrite function suggests that you can write to different sheets. Please clarify what you mean by you cannot do multiple sheets with it. What code are you using, and what exactly are you trying to do?