Attaching callbacks for hscale and optionmenu


I'm building a GUI with gtk+ 1.2.6 and glade 0.5.3 on RedHat 6.1. I am
using the optionmenu and horizontal scale widget. I would like to attach a
callback which is invoked whenever the option in the menu is changed, and
another which is invoked whenever the value of the hscale is changed. 

Could somebody please tell me for which events I should attach the
callback with gtk_signal_connect in order to do this ? I searched the
reference docs, tutorial, and /usr/include/gtk, but couldn't figure it


  Vaibhav Vaish.
