Since you need to work with a template, I believe you will need to use a
third-party component like the one offered by ASPOSE for this.I used it
and it worked very well for this purpose.
Microsoft discourages automating Office applications in server-code.
Alternatively, you could save that template file as html, use
filesystemobject to open a textstream, do your replacements, and write
the result to Response. Depending on the size of the template, this
might work for you.