Tabs with property page

I have a dialog box, which has 4 different tabs. Those tabs are derived from the CPropertyPage. Inside the dialog box I have 4 buttons, OK, Cancel, Apply, and Help.
Depending on which tab I am in after I push the Apply button the apply button is disabled or reenabled.
Is there anybody know how to enable the apply button all the time?

Thanks,

Suehyun Chung

In order to enable the apply button call SetModified(true).

For further details lookup help for CPropertyPage::SetModified()
in VC++ documentation.