[h-e-w] Different task bar icons?

[Thomas Johnsson]

I often find myself having a large number of icons on the taskbar, many of 
which 
are emacs frames, of which one is the VM frame I'm looking for...

Is it possible to have different taskbar icons for different emacs frames?

Especially, I'd like feature for the VM frame. Even better would be if the
icon could be different depending on whether I have unread mail or not.

-- Thomas