Type
   TCrackDBNi=class(TDBNavigator);


procedure TForm1.Button1Click(Sender: TObject);
var
   CrackDBNi: TCrackDBNi;
   I: TNavigateBtn;
begin
   CrackDBNi :=TCrackDBNi(DBNavigator1);

   for I := Low(CrackDBNi.Buttons) to High(CrackDBNi.Buttons) do
   begin
      if not CrackDBNi.Buttons[i].Enabled then
      begin
         Case i of
            nbFirst  :Showmessage('First   Disable');
            nbPrior  :Showmessage('Prior   Disable');
            nbNext   :Showmessage('Next    Disable');
            nbLast   :Showmessage('Last    Disable');
            nbInsert :Showmessage('Insert  Disable');
            nbDelete :Showmessage('Delete  Disable');
            nbEdit   :Showmessage('Edit    Disable');
            nbPost   :Showmessage('Post    Disable');
            nbCancel :Showmessage('Cancel  Disable');
            nbRefresh:Showmessage('Refresh Disable');
         end;
      end;
   end;
end;