, Ctrl + T TabSheets PageControl, Ctrl + T, :
procedure TForm1.actNextPageExecute(Sender: TObject)
var
nextPageIndex: Integer;
begin
nextPageIndex := PageControl1.ActivePageIndex+1;
if (nextPageIndex > PageControl1.Pages.Count-1) then
nextPageIndex := 0;
PageControl1.ActivePageIndex := nextPageIndex;
end;