Power query overwrites any data it has output when close and load. Suggest you may want to link your out put to a new sheet where you can have the data in native excel and then add your calculations. Then when the PQ is refreshed it only overwrites the output and not the linked range.
@alansidmanDon't know. Suggest you load your workbook and query to a third party URL. Make sure that your data has been anonymized to protect confidential information. Suggest Dropbox.Com or Box.Net