Dan,
This is a guess on how to this as I have not tested this idea.
I would think the text file would need to be saved into the same directory that the webserver runs from. By default, this is 'www' under your LabVIEW directory. With the file saved there, or to a directory under that, you should be able to use the TCI/IP functions to point to it using a relative path and have a button to download the file.
This might at least give you a place to start if it doesn't quite do it.
Ed

Ed Dickens - Certified LabVIEW Architect
Lockheed Martin Space
Using the Abort button to stop your VI is like using a tree to stop your car. It works, but there may be consequences.