void CXTSplitterWndEx2::StartTracking(int ht)
{
    CXTSplitterWndEx::StartTracking(ht);

    // horizontal splitter, undocumented Microsoft values
    if (ht >= 101 && ht <= 115) 
    {
        m_rectLimit.top += m_nMin;
        if (m_nMax != 0)
            m_rectLimit.bottom -= (m_rectLimit.bottom - m_nMax);
    }
    // vertical splitter, undocumented Microsoft values
    else if (ht >= 201 && ht <= 215)
    {
        m_rectLimit.left += m_nMin;
        if (m_nMax != 0)
            m_rectLimit.right -= (m_rectLimit.right - m_nMax);
    }
}

.H file

class CXTSplitterWndEx2 : public CXTSplitterWndEx
{
public:
    CXTSplitterWndEx2();

    virtual void           SetColors                      (COLORREF crTL, COLORREF crBR, COLORREF crInside);
    virtual void           SetMinMax                      (UINT nMin, UINT nMax);
    virtual void           OnDrawSplitter                   (CDC* pDC,ESplitType nType, const CRect& rectArg);
    virtual void           StartTracking                   (int ht);

protected:
    COLORREF               m_crTopLeft, m_crBottomRight,m_crInside;
    UINT                   m_nMin, m_nMax;
};



.CPP file

CXTSplitterWndEx2::CXTSplitterWndEx2()
{
    m_crTopLeft = RGB(255, 255, 255);
    m_crBottomRight = RGB(173, 170, 156);
    m_crInside = RGB(239, 235, 222);
    m_nMin = m_nMax = 0;
}

void CXTSplitterWndEx2::SetMinMax(UINT nMin, UINT nMax)
{
    m_nMin = nMin;
    m_nMax = nMax;
}

void CXTSplitterWndEx2::SetColors(COLORREF crTL, COLORREF crBR, COLORREF crInside)
{
    m_crTopLeft = crTL;
    m_crBottomRight = crBR;
    m_crInside = crInside;
}

void CXTSplitterWndEx2::StartTracking(int ht)
{
    CXTSplitterWndEx::StartTracking(ht);

    // horizontal splitter, undocumented Microsoft values
    if (ht >= 101 && ht <= 115) 
    {
        m_rectLimit.top += m_nMin;
        if (m_nMax != 0)
            m_rectLimit.bottom -= (m_rectLimit.bottom - m_nMax);
    }
    // vertical splitter, undocumented Microsoft values
    else if (ht >= 201 && ht <= 215)
    {
        m_rectLimit.left += m_nMin;
        if (m_nMax != 0)
            m_rectLimit.right -= (m_rectLimit.bottom - m_nMax);
    }
}

void CXTSplitterWndEx2::OnDrawSplitter(CDC* pDC, ESplitType nType, const CRect& rectArg)
{
    if (pDC == NULL)
    {
        RedrawWindow(rectArg, NULL, RDW_INVALIDATE | RDW_NOCHILDREN);
        return;
    }

    ASSERT_VALID(pDC);

    if (nType == splitBar)
    {
        CRect    rect = rectArg;
        // Draw outside of rectangle.
        pDC->Draw3dRect(rect, m_crTopLeft, m_crBottomRight);
        rect.InflateRect(-GetSystemMetrics(SM_CXBORDER), -GetSystemMetrics(SM_CYBORDER));
        // Draw inside of rectangle.
        pDC->FillSolidRect(rect, m_crInside);
        return;
    }
}