How do you prevent a new event handling to start when an event handling is already running?

I press a button1 and event handler start e.g. slow printing job. There are several controls in form buttons, edits, combos and I want that a new event allowed only after running handler is finnished.

I have used fRunning variable to lock handler in shared event handler. Is there more clever way to handle this?

procedure TFormFoo.Button_Click(Sender: TObject);    
begin
  if not fRunning then
  try
    fRunning := true;
    if (Sender = Button1) then // Call something slow ...
    if (Sender = Button2) then // Call something ...
    if (Sender = Button3) then // Call something ...
  finally
    fRunning := false;
  end;
end;