How can I create a list of the files in a Windows directory?

Right. Actually, once the remote file system is mounted to the Eggplant machine, you can also use any of the SenseTalk file and file system access mechanisms described in chapter 14 of the SenseTalk Reference manual.

So, in your case you might do something like this:

put files("/mounted/path/to/remote/directory") into fileList

repeat with each filename in fileList
    click "appFilenameField"
    typeText filename & return
end repeat