You must set the Property Page's Changed
property to True in order to
enable the Apply button on the Property Page.
The most appropriate place to set the Changed property
is in the corresponding event procedures of the controls you've placed on the Property
Page for editing the values of properties.
For example, if a TextBox control on your Property
Page represents the value of a property, you would set the
Changed property in the TextBox control's
Changed event procedure. Again, if an OptionButton
control represents a property value, then you'd set the
Changed property to True in its Click event