Handling scripted commands in Firefox

I'm trying to create a web page that plays a video and changes an
associated image via script commands in the video. I've got everything
working for Internet Explorer, but so far I'm only able to play the
video in Firefox (I'm using the Windows Media plugin for Firefox, not
the ActiveX control).

I'm using the NPDS.npDSEvtObsProxy applet to try and redirect the
ScriptCommand event, but I haven't gotten anything from it. It took me
a while to get the applet to load, and now when it loads it takes up
100% of the cpu and freezes the browser. Has anyone successfully
handled ScriptCommand events in Firefox without using the ActiveX control?

Thanks in advance,
Chris