var
  SX: Integer = -1;
  SY: Integer = -1;

procedure Point1Set(X, Y: Integer);
begin
  SX := X;
  SY := Y;
end;

procedure Move(Sender: TObject; X, Y: Integer);
begin
  if SX >= 0 then
  begin
    TControl(Sender).Left := TControl(Sender).Left - (SX - X);
    TControl(Sender).Top := TControl(Sender).Top - (SY - Y);
  end;
end;

procedure TForm3.MouseDown(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
begin
  Point1Set(X, Y);
end;

procedure TForm3.MouseMove(Sender: TObject; Shift: TShiftState; X, Y: Integer);
begin
  Move(Sender, X, Y);
end;

procedure TForm3.MouseUp(Sender: TObject; Button: TMouseButton; Shift: TShiftState; X, Y: Integer);
begin
  Point1Set(-1, -1);
end;