Hey all. I\'ll try to make this brief and simple. :)
I have
You might consider an XML based approach.
Word has a feature called Custom XML data-binding, or data-bound content controls. A content control is essentially a point in the document which can contain content. A "data-bound" content control gets its content from an XML document you include in the docx zip file. An XPath expression is used to say which bit of XML. So all you need to do is include your XML file, and Word will do the rest.
Excel has ways to get data out of it as XML, so the whole solution should work nicely.
There is plenty of information on content control data-binding on MSDN (some of which has been referenced in earlier SO questions) so I won't bother including them here.
But you do need a way of setting up the bindings. You can either use the Content Control Toolkit, or if you want to do it from within Word, my OpenDoPE add-in.