How to detect when user scrolls

[Andrew Wood <a j w me com>]

Im writing some code which will call a function (userActive) when the 
user does something, for mouse moves, clicks and keyboard presses this 
is working fine:

g_signal_connect(G_OBJECT(mainwindow),"motion-notify-event",G_CALLBACK(userActive),NULL); 
//will be called when a mouse move occurs
g_signal_connect(G_OBJECT(mainwindow),"button-press-event",G_CALLBACK(userActive),NULL); 
//will be called when a mouse click occurs
g_signal_connect(G_OBJECT(mainwindow),"key-press-event",G_CALLBACK(userActive),NULL); 
//will be called when a key press occurs

However in the mainwindow is a GtkScrolledWindow, and although its 
detecting mouse movement over the display area, if the user is just 
moving the scrollbarsandnot doing anything else, as they would if 
reading through some text, it doesnt detect it.

I've tried the following, on both the GtkScrolledWindow 
(browserscrolledview) and the mainwindow (GtkWindow) but to no avail:

g_signal_connect(G_OBJECT(browserscrolledview),"scroll-event",G_CALLBACK(userActive),NULL); 
//will be called when user scrolls in display area

How do I detect when the scrollbars move?

Thanks