Hi Bob,

Thanks very much for your feedback!

I think I am not fully understand your problem. I think you just want to
programmatically control the scroll bar, yes? Does my code snippet of
P/inovke like this work for you?
const int WM_HSCROLL=0x114;
const int SB_THUMBPOSITION=0x4;
const int SB_THUMBTRACK = 0x5;

[DllImport("user32.dll", CharSet=CharSet.Auto)]
static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wParam,
IntPtr lParam);
private void button4_Click(object sender, System.EventArgs e)
{
    SendMessage(this.panel1.Handle, WM_HSCROLL,
(IntPtr)(0x100000000&SB_THUMBPOSITION), IntPtr.Zero);
}
At my side, this code may will scroll the panel horizontally.

Also, we may use Panel's AutoScrollPosition property to control the scroll
position, like this:
private void Form1_Load(object sender, System.EventArgs e)
{
    pt=new Point(this.panel1.AutoScrollPosition.X,
this.panel1.AutoScrollPosition.Y);
}

private Point pt;
private void button5_Click(object sender, System.EventArgs e)
{
    pt=new Point(pt.X +5, pt.Y+5);
    this.panel1.AutoScrollPosition=new Point(pt.X, pt.Y);
} //scroll the horizontally 5 pt and vertically 5 pt.

If I misunderstand you, please feel free to tell me, thanks.

Thank you for your patience and cooperation. If you have any questions or
concerns, please feel free to post it in the group. I am standing by to be
of assistance.

Best regards,
Jeffrey Tan
Microsoft Online Partner Support