[roman]

Usa el mensaje WM_WINDOWPOSCHANGING:

Código Delphi [-]
type
  TForm1 = class(TForm)
  private
    procedure WMWindowPosChanging(var Msg: TWMWindowPosChanging);
      message WM_WINDOWPOSCHANGING;
  end;

implementation

procedure TForm1.WMWindowPosChanging(var Msg: TWMWindowPosChanging);
begin
  inherited;

  {
    Aquí ajustas la posición de Form2
  }
end;

// Saludos