If a user tries to open a Workbook that is already open, then they normally get a message saying that the File is locked by a certain user and would you like to open the file in Read only mode. However, you can open a workbook in shared mode by following these steps. First open the file that you want to share, then once the workbook is open, go to the Tools menu and choose Share Workbook from the drop down menu. The Share Workbook dialog box will now appear. To enable sharing, you simply click once on the Allow Sharing check box, so that it has a tick. Once you do this other people will now be able to use your Excel workbook whilst you are working on it.
Just as with HTML editors, various open-source software programs have sprung up to provide an alternative to the dominant player, Dreamweaver in the case of website editors and Microsoft office in the case of office application suites. Whereas in the webpage authoring arena you have NVU, SeaMonkey and KompoZer, in the office application suite you have LibreOffice (formerly called OpenOffice) and NeoOffice.