XML/Word merge to HTML

This should be simple but I'm struggling to find the solution. Okay, I've got Word documents with MailMerge Fields. I've got XML data. I want to map the XML elements to the MailMerge Fields and convert the resulting document to HTML. Of course the number and order of intermediate steps is irrelevant as long as the process can be automated. In other words I could convert all my Word documents and create style sheets up front.

I have been using XMLSpy to create Schemas for my data and Word documents. I was going to use BizTalk Mapper to create the transforming Stylesheet.