Here you are. Put a RichTextBox on a form and paste the code below to test. You can use this piece of code as my contribution in the codebook also. Let me know if you need any enhancements.

VB Code:
  1. Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.Load
  2.         Dim rtbContextMenu As New ContextMenu()
  3.         Dim mymenuitem As MenuItem
  4.         mymenuitem = rtbContextMenu.MenuItems.Add("Copy")
  5.         AddHandler mymenuitem.Click, AddressOf myCopy_Click
  6.  
  7.  
  8.         mymenuitem = rtbContextMenu.MenuItems.Add("Paste")
  9.         AddHandler mymenuitem.Click, AddressOf myPaste_Click
  10.  
  11.         RichTextBox1.ContextMenu = rtbContextMenu
  12.     End Sub
  13.     Private Sub myCopy_Click(ByVal sender As Object, ByVal e As System.EventArgs)
  14.         Clipboard.SetDataObject(RichTextBox1.SelectedText)
  15.     End Sub
  16.     Private Sub myPaste_Click(ByVal sender As Object, ByVal e As System.EventArgs)
  17.         ' Declares an IDataObject to hold the data returned from the clipboard.
  18.         ' Retrieves the data from the clipboard.
  19.         Dim iData As IDataObject = Clipboard.GetDataObject()
  20.  
  21.         ' Determines whether the data is in a format you can use.
  22.         If iData.GetDataPresent(DataFormats.Text) Then
  23.             ' Yes it is, so display it in a text box.
  24.             RichTextBox1.SelectedText = CType(iData.GetData(DataFormats.Text), String)
  25.         Else
  26.             ' No it is not.
  27.             RichTextBox1.SelectedText = "Could not retrieve data off the clipboard."
  28.         End If
  29.  
  30.  
  31.     End Sub