In MFC MS chart control how to see values of chart points when the mouse is on points?

In any CWnd based class you can override CWnd::OnMouseMove in your derived class:

// In CMyClass header file:
//afx_msg void OnMouseMove(UINT nFlags,  CPoint point);

// In CMyClass source file
BEGIN_MESSAGE_MAP(CMyClass, CBaseClass)
    ON_WM_MOUSEMOVE()
END_MESSAGE_MAP()

void CMyClass::OnMouseMove(UINT nFlags, CPoint point)
{
    // Note that this called repeatedly so that execution should
    //  not consume too much time.

    // Add your code here.
    // Check if the CPoint (relative to the upper-left corner if the CWnd)
    //  is on the chart.
    // If so, calculate the value using the proerties of the chart and display them.

    CBaseClass::OnMouseMove(nFlags, point);
}

If that does not work with the MS Chart Control (I have never used it), you can capture the mouse in your parent window hosting the chart control (see SetCapture() at the above CWnd link). Note that doing so disables all mouse features of the control.

Anyway, I suggest to use one of the many MFC chart control implementations that can be found in the web instead of this ancient control.