Open app e.g. Word then open file via FireFox (for WebDav integration)

I'm writing a custom WebDav integration for our website and in IE I can use new ActiveXObject to open e.g. Word from javascript then open a file. It's got to be like this to enable the applications WebDav integration, I can't just use a link.

We support Firefox as a browser however and new ActiveXObject doesn't work. I've toyed with writing a Silverlight 4 app which apparently can open Word on the user's desktop or even asking the user to download some sort of Console app that launches Word/Excel/etc. I don't want to do this though and I keep thinking someone must have had this issue before.

So.. is there a way to open Word 开发者_Python百科from Firefox FIRST, THEN open a url from Word.

Cheers,

Adam.

UPDATE: Silverlight 4 no longer an option, don't want to use OOB

Not in plain HTML. But a firefox extension should allow this.