title: How to allow or forbid user to enter tab in pagecontrol?
body: <p>I want to restrict users (based on special condition) to open a tab or not in a page control. ie, the user can click on the tab but it will not be displayed to him. Instead, a message will show to him that "<code>he don't have the access right to see such tab</code>".</p>
  
  <p>On what event I should write the checking code, and what tab property (of <code>TPageControl</code> component) will allow/block user to enter such tab?</p>