Challenges with Sharing Excel Workbooks in SharePoint

In Excel 2007 (and 2003), you can share a workbook.  This allows users to simultaneously update the same file:

This feature is used in many enterprises for collaboration, especially in departments such as Finance or Planning where there are lots of shared figures, budgets, plans, etc.

There are some interesting features that allow for some rich collaboration scenarios simply within a single Excel file:

• Each time that you save the shared workbook, you are prompted with the changes that other users have saved since the last time that you saved the shared workbook. If you want to keep the shared workbook open to monitor progress, Excel can update you with the changes automatically, at timed intervals that you specify, with or without saving the workbook yourself.
• When you save changes to a shared workbook, another person who is editing the workbook might have saved changes to the same cells. In this case, the changes conflict, and you are prompted with a conflict resolution dialog box so that you can choose which changes to keep

When moving to SharePoint as a document management platform, this feature is no longer supported:

More than one user cannot simultaneously make changes to a shared workbook that is stored on a Windows SharePoint Services 3.0 site. If you want to store your workbook on a Windows SharePoint Services 3.0 site, you should do so only after the collaboration effort through sharing is complete.

Document libraries by design only allow one person to edit a document at the same time.  In addition, they support check-in and out to provide locks on documents during the editing process.  When a user grabs a file for editing from SharePoint, they edit a file on their local machine and then when done it is saved back to the central document repository. 

Excel Services allows for running of Excel files within the SharePoint server, but only in read only fashion.  Excel Services is great for read only dashboards, charts and graphs but isn’t a collaboration service.

For more information on the different options for Excel collaboration, see Microsoft’s article on the subject.