How to move scroll bar up by one line? (In C# RichTextBox)

using System.Runtime.InteropServices;

[DllImport("user32.dll")]
static extern int SendMessage(IntPtr hWnd, uint wMsg,
                               UIntPtr wParam, IntPtr lParam);

SendMessage(myRichTextBox.Handle, (uint)0x00B6, (UIntPtr)0, (IntPtr)(-1));

RichEdit.SelectionStart = SendMessage(RichEdit.Handle, EM_LINEINDEX, ScrollTo, 0);
RichEdit.ScrollToCaret();