Your post is confusing, at best and whatever you're trying to achieve remains a mystery.
Documents and templates are not the same thing. Mailmerges don't ordinarily use templates - they use mailmerge main documents. Similarly, INCLUDETEXT fields would ordinarily point to documents, not templates.
Furthermore, it is far from clear what relationship exists between what you're calling the 'Mail Merge Template' and the other two 'templates'. You also refer to having the user 'go through the Mail Merge Fields'. To what end?
A mailmerge main document can conditionally insert content from other documents via INCLUDETEXT fields and those fields can themselves reference documents/ranges containing mergefields of their own.
As for your use of DDE, that is seriously outdated technology. Using the OLE DB provider - which is the default for Word 2002 and later - the formatting of the output in Word is independent of the data source format. Amongst other things, that means you don't have to format the data in Excel the way you want it to appear in the output (which can even necessitate having multiple columns with the same data formatted different ways with OLE). The
Mailmerge Tips and Tricks 'Sticky' thread at the top of the Mail Merge forum :
https://www.msofficeforums.com/mail-...ps-tricks.html
shows how field switches can be used to generate a wide variety of formats that are independent of that of the data source.