I have a spreadsheet that lists different operations performed on a work order. Each operation is a different row and the column headers are "Order", "Operation", "Start Date", and "Finish Date". Each order could have as many as 10 rows associated with it. The start times of operations within an order will be sequential but start times of operations of different orders will not be sequential. I would like to sort the rows by order to keep each orders operations grouped together. I would also like to sort the operations within an order by the start date of the operation. So basically, how can I perform nested sorting?