On this page:
http://www.experts-exchange.com/Web/Web_Languages/JavaScript/Q_20233392.html
there's a link to
http://www.krikkit.net/howto_javascript_copy_clipboard.html
which has a script that works in IE as well as FF after you make a change in the prefs.js file... not quite the solution I was looking for, but might be worth a look.
If I come across other hints on how to make this happen in FF or OP I'll jot them down here, too. Would be cool to get this to work in browsers other than IE eventually.