Thanks for your posting and using Aspose.Cells.
Please try the Worksheet.DisplayRightToLeft property and set it true. It should fulfill your needs.
Please see the following sample code. I have attached the output xlsx file generated by it for your reference.
Workbook workbook = new Workbook();
Worksheet worksheet = workbook.Worksheets;
worksheet.DisplayRightToLeft = true;
Thank you so much !