This uses the 'copy' and 'paste' DOM events to trigger a counter update. I haven't had a chance to 100% confirm that middle-button click on X11 triggers the event, but it ought to.
Cut and paste events from context menu and main edit menu known good in:
* Firefox 4.08b-pre
* IE 9 preview 7
* IE 8 current
* Chrome 8 beta current
* Safari 5.0.3
Opera is listed as not supporting these events, oh well.
Note that using a *delete* command from a menu doesn't trigger an event. Sigh, you can't win everything.
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