file upload monitoring

i was trying to achieve file upload notification with a progress bar
using prototype. there is the possibility in helma to have control of
the upload injecting a FileUploadListener that will report the number
of bytes uploaded (and so been able to display a progress meter) ?

been using this in a servlet context, and working nicely:
http://www.missiondata.com/blog/java/28/file-upload-progress-with-ajax-and-java-and-prototype/

have anyone done this in helma or have some ideas or excerpt to start with ?

thanx