If you have a workbook in which you want to allow more than one other person to add or modify data simultaneously, you can set up and save the workbook as "shared" and then make it available on a network share (not a Web server).
As the owner of the workbook, you can prepare it to be shared by entering and formatting the data that needs to be present. When you are finished, click Share Workbook in the Changes group on the Review tab, select your options, and then save the workbook on a network share (not a Web server) that is available to the intended users. Alternatively, you can click Protect and Share Workbook in the Changes group on the Review tab to prevent other users from turning off Change Tracking in the workbook.
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.