Hi Clint
GridView RW is not meant to be used in the normal course of operations unless it is the absolute last resort. There are two better ways to do this directly from SalesAnalysis.
If the number of transactions to modify is low, you can just go into Edit | Sales Data, find the transaction and modify the cost.
If that is too difficult, you can use export/import to make the change. First make a backup. Then export the range of transactions you'll want to modify (date and/or document range) to Excel. Then purge the exact same range under Maintenance | Archive/Purge/Restore Sales Data. Then modify the Excel file and import it back into SalesAnalysis. If you use the View Statistics screen, you'll want to also run Statistics | Rebuild Sales Statistics (you'd want to do this if you used GridView RW too).
Steve