Растягивание формы при нажатии кнопки

void __fastcall TForm1::Button1Click(TObject *Sender)
{
    this->ClientHeight += 100;
}

this->ClientHeight -= 100;

int NormalSize;
bool flag=false;
//---------------------------------------------------------------------------
void __fastcall TForm1::FormCreate(TObject *Sender)
{
    NormalSize=this->ClientHeight;
    Timer1->Enabled=true;
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Timer1Timer(TObject *Sender)
{
    if (flag)
        this->ClientHeight+=5;
    else
        for (;NormalSize<this->ClientHeight;)this->ClientHeight-=5;
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button3Click(TObject *Sender)
{
        this->ClientHeight+=5;
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button3MouseDown(TObject *Sender, TMouseButton Button, TShiftState Shift,
          int X, int Y)
{
    NormalSize=this->ClientHeight;
    flag=true;
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button3MouseUp(TObject *Sender, TMouseButton Button, TShiftState Shift,
          int X, int Y)
{
    flag=false;
}