procedure TForm1.Timer1Timer(Sender: TObject);
begin
 FlashWindow(Application.Handle, True);
end;

Timer1.Interval = n (Tip for n = 1000 "1 second")
 procedure TForm1.Timer1Timer(Sender: TObject);
 begin
  FlashWindow(Handle, true);
  FlashWindow(Application.Handle, true);
 end;

// Define FLASHWINFO structure as record type
type
 FLASHWINFO = record
  cbSize: UINT;
  hWnd: HWND;
  dwFlags: DWORD;
  uCount: UINT;
  dwTimeOut: DWORD;
 end;
 TFlashWInfo = FLASHWINFO;
 // Define dwFlags constants
const
 FLASHW_STOP = 0;
 FLASHW_CAPTION = 1;
 FLASHW_TRAY = 2;
 FLASHW_ALL = FLASHW_CAPTION or FLASHW_TRAY;
 FLASHW_TIMER = 4;
 FLASHW_TIMERNOFG = 12;
var
 Form1: TForm1;
 FWInfo: TFlashWInfo;
 // Function declaration for WinAPI call
function FlashWindowEx(var pfwi: FLASHWINFO): BOOL; stdcall;
 {...}
implementation
{...}
// Import external function from 'USER32.DLL' with the same name
function FlashWindowEx; external user32 Name 'FlashWindowEx';
procedure TForm1.FormCreate(Sender: TObject);
begin
 // Check for API function's availability
 if not Assigned(@FlashWindowEx) then
 begin
  ShowMessage('API Function FlashWindowEx is not present... Exit program!');
  Application.Terminate;
 end
 else
  // Set default parameters
  with FWInfo do
  begin
  cbSize := SizeOf(FWInfo); // Size of structure in bytes
  hWnd := Form1.Handle; // Main's form handle
  dwFlags := FLASHW_ALL; // Flash both caption & task bar
  uCount := 10; // Flash 10 times
  dwTimeOut := 100; // Timeout is 1/10 second apart
  end;
end;
procedure TForm1.Button1Click(Sender: TObject);
begin
 // Flash on normal state
 FlashWindowEx(FWInfo);
end;
procedure TForm1.Button2Click(Sender: TObject);
begin
 // Flash on minimized state
 WindowState := wsMinimized; // Application.Minimize;
 FlashWindowEx(FWInfo);
end;