TTrackBar에는 마우스에 대한 이벤트가 없습니다.
그래서, 상속 받아서 만들어 봤습니다.

//--- Unit1.h ---
//---------------------------------------------------------------------------

#ifndef Unit1H
#define Unit1H
//---------------------------------------------------------------------------
#include <Classes.hpp>
#include <Controls.hpp>
#include <StdCtrls.hpp>
#include <Forms.hpp>
#include <ComCtrls.hpp>
//---------------------------------------------------------------------------
class TMyTrackBar : public TTrackBar
{
__published:
    __property OnMouseDown;
    __property OnMouseUp;
    public:
    __fastcall TMyTrackBar(HWND ParentWindow) : TTrackBar(ParentWindow){}
};
//---------------------------------------------------------------------------
class TForm1 : public TForm
{
__published:    // IDE-managed Components
    TButton *Button1;
    void __fastcall FormCreate(TObject *Sender);
private:    // User declarations
    TMyTrackBar *myTB1;
    void __fastcall MyTrackBarMouseUp(TObject *Sender,TMouseButton Button,
     TShiftState Shift, int x, int y);
public:        // User declarations
protected:
    __fastcall TForm1(TComponent* Owner);
};
//---------------------------------------------------------------------------
extern PACKAGE TForm1 *Form1;
//---------------------------------------------------------------------------
#endif


// --- Unit1.cpp ---
//---------------------------------------------------------------------------

#include <vcl.h>
#pragma hdrstop

#include "Unit1.h"
//---------------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
    : TForm(Owner)
{

}
//---------------------------------------------------------------------------
void __fastcall TForm1::MyTrackBarMouseUp(TObject *Sender,TMouseButton Button,
     TShiftState Shift, int x, int y)
{
   ShowMessage("Good");
}
//---------------------------------------------------------------------------
void __fastcall TForm1::FormCreate(TObject *Sender)
{
    myTB1 = new TMyTrackBar(Form1);
    myTB1->Parent = Form1;
    myTB1->Left = 100;
    myTB1->Top = 100;
    myTB1->OnMouseUp = MyTrackBarMouseUp;
}
//---------------------------------------------------------------------------


건승을 빕니다.


김정현 님이 쓰신 글 :
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: VC++의 Slider에 있는 ReleasedCapture 이벤트 같은 slider를 움직이다가 멈췄을 경우에만
: 발생하는 이벤트는 없나요?
:
: 도와주삼~~~~ ㅠㅠ