Overriden MouseDown event doesn't work well (C++ Builder, Delphi)

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C++

Delphi

C++Builder

Hello! I'm writing a control that inherits from ListView. I need to override MouseDown propertie. To do this I am writing nex declaration in the class of my component:

public:
DYNAMIC void __fastcall MouseDown(System::Uitypes::TMouseButton Button, System::Classes::TShiftState Shift, int X, int Y);

and realization:

void __fastcall TMyListView::MouseDown(System::Uitypes::TMouseButton Button, System::Classes::TShiftState Shift, int X, int Y)
{
     if(Items->Count > 0 && ItemIndex != -1)
     {
	 Beep(1000, 300);
     }
}

As a signal when mouse pressed on item I use Beep() function. But Beep sounds when mouse was upped, i.e. was made a full click. And there is a problem.
How to fix this? I do not need to override SelectItem event because it occurs when item selected or unselected only. I need to handle the mouse pressing.
Please help to solve my problem.