capi:list-panel & callbacks

Hi list,

I'm using a capi:list-panel pane with :interaction set to
:extended-selection.

I need to update a dependent pane when a selection, extension or retraction
is made to the list-panel. But this update is heavy, so I want to do it only
once per select-extend-retract user gesture.

Example : list-panel with 4 items '("one" "two" "three" "four")
---------
user click on "one"  ==> update dependent pane
user press SHIFT+END ==> update dependent pane only once
                         (by using extend-callback, it would have been
updated three times)

Does anybody knows how I can do that ?
TIA,
Sebastien.