--- ---

In many situations you might like to detect if an application is blocked. For example while automating Internet Explorer, you'd like to know if Internet Explorer has stopped responding. 

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms,
  Dialogs, ComObj, StdCtrls;

type
  TForm1 = class(TForm)
    btnLaunch: TButton;
    btnCheck: TButton;
    btnKill: TButton;
    procedure btnLaunchClick(Sender: TObject);
    procedure btnCheckClick(Sender: TObject);
    procedure btnKillClick(Sender: TObject);
  public
    modObjIE : OLEVariant;
    modlngWndIE : THandle;
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

procedure TForm1.btnLaunchClick(Sender: TObject);
begin
  modObjIE := CreateOleObject('InternetExplorer.Application');
  modObjIE.Visible := true;
  modObjIE.Navigate2('https://www.borland.com');
  modlngWndIE := modObjIE.hwnd;
end;

procedure TForm1.btnCheckClick(Sender: TObject);
var
 dwResult : DWORD;
 lngReturnValue : longint;
begin
  lngReturnValue := SendMessageTimeout(
    modlngWndIE, WM_NULL, 0, 0,
    SMTO_ABORTIFHUNG OR SMTO_BLOCK, 1000, dwResult
  );
  if lngReturnValue > 0 then
    ShowMessage('Responding')
  else
    ShowMessage('Not Responding');
end;

procedure TForm1.btnKillClick(Sender: TObject);
var
 ProcessID : DWORD;
 Process : THandle;
begin
  GetWindowThreadProcessId(modlngWndIE, @ProcessID);
  Process := OpenProcess(PROCESS_ALL_ACCESS, false, ProcessID);
  TerminateProcess(Process, 0);
end;

end.

Although the code is written for Internet Explorer, the idea can be used for other applications as well: 

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Classes, Graphics, Controls, Forms,
  Dialogs, StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure Button1Click(Sender: TObject);
  end;

var
  Form1: TForm1;

implementation

{$R *.DFM}

procedure TForm1.Button1Click(Sender: TObject);
var
  H : THandle;
  lngReturnValue : longint;
  DWResult : DWORD;
begin
  H := FindWindow('Notepad', nil);
  if H > 0 then
  begin
    lngReturnValue := SendMessageTimeout(
      H, WM_NULL, 0, 0, SMTO_ABORTIFHUNG And SMTO_BLOCK,
      1000, DWResult
    );
    if lngReturnValue > 0 then
      ShowMessage('Responding')
    else
      ShowMessage('Not responding');
  end
  else
    ShowMessage('Application not found');
end;

end.