signal of scrollbar which is in scrolledwindow

[xiening <xiening topshine com cn>]

hi, sir
in gtk1.2.1
I make a scrolledwindow  by
******************************************
   scrolledWindow = gtk_scrolled_window_new (NULL, NULL);
******************************************
I want something will be done (signal) while the scrolledbar move up and 
down.
I did not find any signal suitable for this purpose.

even
*************************************************************
  gtk_signal_connect (GTK_OBJECT (scrolledWindow), "state_changed",
                   GTK_SIGNAL_FUNC (on_scrolledwindow_state_changed),
                   NULL);
************************************************************
and
*****************************************************************
GtkAdjustment * adjustment;
adjustment = gtk_scrolled_window_get_hadjustment ( GTK_SCROLLED_WINDOW 
scrolledWindow);
gtk_signal_connect (GTK_OBJECT (adjustment), "changed",
                   GTK_SIGNAL_FUNC (on_scrolled_bar_changed),
                   NULL);
**********************************************************
do not work any.
how to deal with this problem?
thank a lot
xn