Control user change of SpinButton value

["Josepo Urrutia" <find_all hotmail com>]

I've some Gtk::SpinButton in my application and I need to control when the 
user change the values of those spinbuttons.

If I use the Gtk::SpinButton::signal_value_changed I can do a callback 
whenever the value of a spinbutton is changed, the problem is that this 
callback is also fired if the value is changed by the code not only by the 
user.

Using the Gtk::Entry::signal_activate makes me able to know when the user 
has enter a value hitting the return key but not by using the mouse over the 
"up/down" buttons.

I've tried with some more signal has Gtk::Widget::signal_button_release but 
no luck.

Is there a simple way to know when the user has change a value of a 
spinbutton?, or to be more expecific when the "up/down" buttons had been 
pressed?