[[escafandra]]

Fijate en el tipo LARGE_INTEGER:

typedef union _LARGE_INTEGER {  
    struct {
        DWORD LowPart;  
        LONG  HighPart; 
    };
    LONGLONG QuadPart;
} LARGE_INTEGER;

Visto esto tienes dos opciones:
Opción 1:

void __fastcall TForm1::Button1Click(TObject *Sender)
{
   LARGE_INTEGER freq;
   LARGE_INTEGER startTime, endTime;
   LARGE_INTEGER elapsedTime, elapsedMilliseconds;
   QueryPerformanceFrequency(&freq);
   QueryPerformanceCounter(&startTime);
   // run code here
   QueryPerformanceCounter(&endTime);
   elapsedTime.QuadPart = endTime.QuadPart - startTime.QuadPart;
   elapsedMilliseconds.QuadPart = (1000 * elapsedTime.QuadPart) / freq.QuadPart;
}

Opción 2, quizás mas clara:

void __fastcall TForm1::Button1Click(TObject *Sender)
{
   LONGLONG freq;
   LONGLONG startTime, endTime;
   LONGLONG elapsedTime, elapsedMilliseconds;
   QueryPerformanceFrequency((LARGE_INTEGER*)&freq);
   QueryPerformanceCounter((LARGE_INTEGER*)&startTime);
   // run code here
   QueryPerformanceCounter((LARGE_INTEGER*)&endTime);
   elapsedTime = endTime - startTime;
   elapsedMilliseconds = (1000 * elapsedTime) / freq;;
}

Saludos.