Compiling Sass files in NetBeans without Maven - Valo theme not found

Hi all,

I'm trying to integrate some Vaadin tech into an existing non-Vaadin project (built using Ant/NetBeans).  I've managed to get a "Hello World" page to appear, but it currently has no theming.  I have the standard starting theme, "mytheme", which does nothing except import the built-in Valo theme.  I've install Sass, and configured the project to automatically compile Sass files on save.  When I edit a Sass file, I get the following error:

"C:\Ruby23\bin\sass.bat" "--cache-location" "C:\Users\archiem\AppData\Local\NetBeans\Cache\8.2\sass-compiler" "C:\src\mywebapp\web\VAADIN\themes\mytheme\styles.scss" "C:\src\mywebapp\web\VAADIN\themes\mytheme\styles.css"
Error: File to import not found or unreadable: ../valo/valo.scss.
        on line 30 of C:/src/mywebapp/web/VAADIN/themes/mytheme/mytheme.scss
        from line 1 of C:\src\mywebapp\web\VAADIN\themes\mytheme\styles.scss
  Use --trace for backtrace.
Done.

mytheme.scss contains the line: @import "../valo/valo.scss";

It's completely understandable that Sass can't find this file, because there is no "valo" folder in "themes".
There is a JAR called vaadin-themes-7.7.6.jar, containing the package "VAADIN.themes.valo", I assume this is what Sass needs.  What is the best way to make this resource available to Sass?

Thanks!
Archie