// Import BlockInput function form user32.dll:

function BlockInput (fBlockInput : boolean) : DWord; stdcall; external 'user32.DLL';

{block input/ blockieren}

procedure TForm1.Button1Click(Sender: TObject);
begin
BlockInput(true);
end;

{unblock input / Blockierung aufheben}

procedure TForm1.Button2Click(Sender: TObject);
begin
BlockInput(false);
end;


Note: Requires Windows 98/2000 or later.
You can unblock input by pressing
CTRL+ALT+DEL