I would like for my students to collaboratively collect some data and add it to an Excel spreadsheet. Is it possible for students to simply login to Blackboard and add their data to an existing spreadsheet without downloading the file and then submitting their updates to me?
If you are indeed looking for students to collaboratively add data to a shared spreadsheet "within" Blackboard, the most efficient and effective way may be to use Google Spreadsheets (http://spreadsheets.google.com) to set up your Excel spreadsheet there and then just have a link to the spreadsheet for students to access from within Blackboard.
After setting up the spreadsheet on Google Spreadsheets, post the URL for the spreadsheet in Blackboard. You and your students will need to each have a free Google account in order to be able to log in to the spreadsheet to make changes. Google Spreadsheet keeps track of version changes, so you can see who is making changes and undo them if necessary. If you prefer, you can upload your existing Excel file right into a Google spreadsheet.