In the ODC 2008, I gave a demo of how to use Excel Web Services from a VBA client - the demo was basically just a managed library that wrapped a generated Web Services proxy.
Since Microsoft no longer seems to supply a SOAP toolkit for office, this is the easiest way of achieving access to Excel Web Services.
The library gives access to all of the important methods exposed by EWS and will allow users to read data/set data and otherwise manipulate an Excel Services session. The following VBA example shows how to use the library:
As you can see, the major difference between the way the library works and the EWS works is that the Session ID is wrapped so that it doesn't need to be used over and over again - as well as that annoying status array that's usually ignored.
I have published the library on MSDN Code Samples - it's called EwsCom - enjoy.