[Code]

var

  MD5Comp: string;

procedure ExitProcess(uExitCode:UINT);

  external 'ExitProcess@kernel32.dll stdcall';

procedure CurStepChanged(CurStep: TSetupStep);

begin

  MD5Comp := '32297BCBF4D802298349D06AF5E28059';

  if CurStep = ssInstall then

  begin

   if MD5Comp <> GetMD5OfFile(ExpandConstant('{app}\cg.npa')) then

   begin

     MsgBox('A patched version detected. Setup will now exit.', mbInformation, MB_OK);

     ExitProcess();

   end;

  end;

end;