If you use CPropertySheet, the callback proc will always be AfxPropSheetCallback which setting by MFC (have a look to Mfc\Src\DlgProp.cpp please).Override the OnInitDialog() will be the most simple way to do extra initializtion.Of cause you can use the API PropertySheet() to implement your callback if you want to write many many code...
P.S. I don't think there has any trouble to do a class for a point member.