CScrollView滚动条范围问题 超过32位不能正确下拉问题

BOOL CMyScrollView::OnScroll(UINT nScrollCode, UINT nPos, BOOL
bDoScroll)
{
SCROLLINFO info;
info.cbSize = sizeof(SCROLLINFO);
info.fMask = SIF_TRACKPOS;

if (LOBYTE(nScrollCode) == SB_THUMBTRACK)
{
GetScrollInfo(SB_HORZ, &info);
nPos = info.nTrackPos;
}

if (HIBYTE(nScrollCode) == SB_THUMBTRACK)
{
GetScrollInfo(SB_VERT, &info);
nPos = info.nTrackPos;
}

return CScrollView::OnScroll(nScrollCode, nPos, bDoScroll);
}