How to make a single cell editable in Gtk::TreeView?

[Gerardo Ballabio <gerardo ballabio gmail com>]

Hi all,
may I ask your help.

I'm trying to build a "best scores" dialog for a game I'm developing,
using a Gtk::TreeView with a Gtk::ListStore model.  When a player sets
a score that ranks within the best, a new entry must be added, and the
player must be able to write his name into that entry, but must not be
allowed to edit other existing entries.

That is, I need to make only a single cell editable.  In the
documentation and the examples I found how to make entire columns
editable, but couldn't understand how to make a single cell editable.
Can you please explain how to do that?

Thanks
 Gerardo