Eventbox for toolbuttons

[<jimenezr ufrima imag fr>]

Hello

I'm trying to change a toolbutton which should be diffent than other
toolbutton.
After trying to change the style with no sucess, I'm trying to use an
eventbox,adding the toolbutton on the eventbox and change the color of the
eventbox.
My working code without eventbox is simple like:
  toolbutton = Gtk::manage(new Gtk::ToolButton("test"));
  toolbar.append(*toolbutton);
 ...

and I'm trying to change it in:
   toolbutton = Gtk::manage(new Gtk::ToolButton("test"));
   m_EventBox  = new Gtk::EventBox();
   m_EventBox->add(*toolbutton);
   toolbar.add(*m_EventBox);
   toolbar.append(*toolbutton); // We can't use
toolbar.append(*m_EventBox)                                               
     
                                // directly
 ...
but the toolbar is not show 

I've no problem to use eventbox for other widget like label or toolbar.
Is it possible to use eventbox for toolbuttons in a toolbar?

If someone could explain me what I'm doing wrong...

Thanks in advance

Remy