Unlike the rest of the XML functionality in Word, Excel, and Access, if you want to use SOAP-based web services, you'll need to download a separate package, the Microsoft Office Web Services Toolkit. (InfoPath has web services support built into it.) As the URL for this package has changed a few times, it's easiest to go to http://www.microsoft.com/downloads/search.aspx and search for "Office Web Services Toolkit." Separate versions are available for Office XP and Office 2003. Once you've installed it, you'll be able to have Office generate VBA code for accessing and using web services. Microsoft's support for SOAP comes with the toolkit, and has also become part of Windows with Windows XP.
Unlike the other XML features described in this book, using the Microsoft Office Web Services Toolkit works the same way across applications, except for InfoPath. Once you've learned how to interact with a web service in Excel, you can use the same code to work with it in Word or Access. The only thing that needs to change is the integration between your VBA code and the object model for the particular application and document you're working with. It's probably easiest to start your development in Excel, as the Excel grid makes it easy to set up test environments where inputs occupy particular cells and outputs are placed into particular cells by the VBA code.