Export ALV output table to an XXL file

I am after writing a new report (ZMYPROGRAM) which is a copy of RKKBCAL2. I have added new fields so now my output is 186 columns wide. When I use the List>Export>Local File, it presents me with the options to save as unconverted, spreadsheet, rich text format etc.... However, when I choose spreadsheet and generate the file, my header lines are wrappped around and the output is skewed. I have seen in SE16N, MARA table that I can choose Export>Spreadsheet>Excel (in Existing XXL Format) and that can handle 231 columns. Is there a tutorial somewhere that I can see how to enable exporting an ALV output table to an XXL file from a custom report?

Thanks!

Julie