const
  FWidthMin = 300;
  FHeightMin = 200;
  FWidthMax = 600;
  FHeightMax = 400;

procedure TForm1.FormResize(Sender: TObject);
begin
  if (FHeightMax > 0) and (Self.Height > FHeightMax) then
  begin
    Self.Height := FHeightMax;
    Self.BorderStyle := TFmxFormBorderStyle.bsSingle;
    Self.BorderStyle := TFmxFormBorderStyle.bsSizeable;
    // Mouse_Event(MOUSEEVENTF_ABSOLUTE or MOUSEEVENTF_LEFTUP, 0, 0, 0, 0);
  end;

  if (FHeightMin > 0) and (Self.Height < FHeightMin) then
  begin
    Self.Height := FHeightMin;
    Self.BorderStyle := TFmxFormBorderStyle.bsSingle;
    Self.BorderStyle := TFmxFormBorderStyle.bsSizeable;
    // Mouse_Event(MOUSEEVENTF_ABSOLUTE or MOUSEEVENTF_LEFTUP, 0, 0, 0, 0);
  end;

  if (FWidthMax > 0) and (Self.Width > FWidthMax) then
  begin
    Self.Width := FWidthMax;
    Self.BorderStyle := TFmxFormBorderStyle.bsSingle;
    Self.BorderStyle := TFmxFormBorderStyle.bsSizeable;
    // Mouse_Event(MOUSEEVENTF_ABSOLUTE or MOUSEEVENTF_LEFTUP, 0, 0, 0, 0);
  end;

  if (FWidthMin > 0) and (Self.Width < FWidthMin) then
  begin
    Self.Width := FWidthMin;
    Self.BorderStyle := TFmxFormBorderStyle.bsSingle;
    Self.BorderStyle := TFmxFormBorderStyle.bsSizeable;
    // Mouse_Event(MOUSEEVENTF_ABSOLUTE or MOUSEEVENTF_LEFTUP, 0, 0, 0, 0);
  end;
end;