Tree Control with checkboxes

[ABCD]

Hello,

I'm working under windows NT , VC++.

I'm working on A Tree control(CTreeCtrl) which has checkbuttons.
You can enable Tree Control to include checkbuttons
by enabling the "checkbuttons" property.

Normally this checkbuttons ( inside the Tree control )
have only two states.
Is it possible to define a third state ?
The state i want to define is when the chekbox is marked
and its color is grey.

Another question is , How can i activate a function when
a user check ( marks ) the checkboxes ?

I want to write a callback function that will be activated
when the checkbox in the list controlled will be marked
(checked). is this possible ?



Thanks,
Ronen