I ran into a similar problem using Totara, Moodle's cousin. I had an activity for pre, post, and open feedback (comments) for each course. I would export the results from each activity into an Excel spreadsheet from the Analysis tab with the raw data, giving me three spreadsheets. Using VBA in Excel I created forms and macros to merge the three spreadsheets, format them, analyze the data, and create a new worksheet with comparison results and charts. Yes, it is the long way around, but it works.