I use Visual Basic and an automation interface to retrieve strings from an external application. These strings contain simple html formatting codes (, , et
Here's a link to add HTML to the clipboard using VB:
http://support.microsoft.com/kb/274326
Once you have the HTML on the clipboard, paste it into your word doc using something like this:
ActiveDocument.Range.PasteSpecial ,,,,WdPasteDataType.wdPasteHTML
This is pretty much the equivalent of you cutting and pasting it in manually.