Could you attach a sample workbook? Screenshots or additional explanation to better understand what you're looking for?
This is possible if you create a calculated field that identifies when each comment should come up, a case statement, and place the comment field on the Label shelf. Alternatively, if the comments are not in a data field, you could create a sheet with each of the comments and then swap sheets using a parameter. These are just flying blind ideas. You really should post a sample for people to work with.