Visual Studio Tools for Office
No, it's not. Data caching is added to document-level customizations through the VSTO Designer. It's not available otherwise.
Of course, you can access most parts of an Excel workbook through a data connection (OLE DB or Jet Engine ODBC)...
Adding to the comments given by Cindy, she is basically right, there are however some working methods that allow you to make things work.
What you could do is create a Template with VSTO containing several cache entries to your own liking and have another addin create documents based on this template. After creating the document containing the cache entries you can access these cache objects through the ServerObject interface. When the document is then opened the data is available to work with.
I'm not sure this fits in your scenario and hope I gave you some hints here to get you going ...
-= Maarten =-
255 Characters. Excel doesn't appear to generate an error if you try to save more, but when you query the property only 255 characters are returned...