Could a timestamp and username be automatically added when an Excel file is refreshed via the add-in? This way the end user or another person who opens a workbook knows the last time the file was refreshed and who carried out that refresh? This also would help with version control.
Easy way to segregate the two is by creating a separate view. One for the current month and the other for the current quarter. You can refer them upon the connection definition.
Hope that helps.