Markbook bulk mark entry

I have created markbook columns for a bulk of classes, uploaded the file and then went to a specific class to export the list of students for a specific class. I was wondering if there was a way of uploading that spreadsheet back onto the system, once I fill in the grades for this class. The MarkbookMarks file has a totally different design and I would have to spend a lot of time changing the usernames. Also not sure how to specify the Term for which I want the marks to be updated? Thank you