GtkCombo drop-down list signals?!?

[Stephan Haller <nomad cadoritz de>]

Hey,

Is there any possiblity to catch a signal for a combo-box which
selection was changed only by the drop-down list? I have a combo box
filled with some values (e.g. 5 values) and I want to react if the
combo-box's entry (text box) was changed via the drop-down list and only
if selection was done. That means not getting all these selection
changed signal while drop-down list is visible and user selects via the
cursor keys or entry (text box) is directly changed by entering text and
pressing ENTER.

Is there any signal or many signals?

Please remember I'm a newbie and I'm glad to know (I think so ;) how to
use signals.

Thanks 

Stephan Haller