Change property pages:urgent

I created a project used CPropertySheet and CPropertyPage. When page changing, I need to save previous page's data and transfer it to another application.
I don't know how to work on select changing event with CPropertySheet derived object. CTabctrl object has TCN_SELCHANGE event. We can add the function
corresponding to this event. is there anybody know how to do it with propery pages change?
I appreciate any reply! Thanks a lot!

Override the CPropertyPage function OnKillActive which is called when the current page is no longer made active, such as when you have switched to a different page.