VB.NET Richtextbox控件联动
两个Richtextbox控件（内容不同），如何实现托动其中一个控件的滚动条或鼠标时另一个Richtextbox控件的内容也随着同步移动。请各位高手帮助解决，要代码。谢谢！！
程序代码：
Public Class Form1
Const EM_LINESCROLL = &HB6
Private Declare Function SendMessageBynum Lib "user32" Alias "SendMessageA" (ByVal hwnd As Integer, ByVal wMsg As Integer, ByVal wParam As Integer, ByVal lParam As Integer) As Integer
Public Function GetFirstLine() As Integer
Dim point As System.Drawing.Point
point.Y = 1
point.X = 1
Dim start As Integer = RichTextBox1.GetCharIndexFromPosition(point)
GetFirstLine = RichTextBox1.GetLineFromCharIndex(start)
End Function
Private Sub RichTextBox1_VScroll(ByVal sender As Object, ByVal e As System.EventArgs) Handles RichTextBox1.VScroll
RichTextBox2.ScrollToCaret()
SendMessageBynum(RichTextBox2.Handle, EM_LINESCROLL, 0, GetFirstLine)
End Sub
End Class