Danl:
I have not heard of anyone directly using Excel to call DataExchange, however I have a few churches using macros to create XML from an Excel workbook and then having some process push the data up to DataExchange.
What you're looking for can be done using the script editor and some of the developer soap libraries provided by Microsoft. Last year @ DC07 illustrated the concept using outlook - but the same principles still hold true - see my post on it here. Let me know if you want the code and Office libraries for my illustration.
Bob:
You can download the DataExchange code libraries here to help you accomplish what you’re trying to do.
--Nick