There is, since you handle it:
Code:
Private Function WindowProcControl(ByVal hWnd As Long, ByVal wMsg As Long, ByVal wParam As Long, ByVal lParam As Long) As Long
Select Case wMsg
...
    Case WM_VSCROLL, WM_HSCROLL
        ' The notification codes EN_HSCROLL and EN_VSCROLL are not sent when clicking the scroll bar thumb itself.
        If LoWord(wParam) = SB_THUMBTRACK Then RaiseEvent Scroll
    Case WM_CONTEXTMENU
        If wParam = RichTextBoxHandle Then
            Dim P As POINTAPI, Handled As Boolean
            P.X = Get_X_lParam(lParam)
            P.Y = Get_Y_lParam(lParam)
            If P.X > 0 And P.Y > 0 Then
                ScreenToClient RichTextBoxHandle, P
                RaiseEvent ContextMenu(Handled, UserControl.ScaleX(P.X, vbPixels, vbContainerPosition), UserControl.ScaleY(P.Y, vbPixels, vbContainerPosition))
            ElseIf P.X = -1 And P.Y = -1 Then
                ' If the user types SHIFT + F10 then the X and Y coordinates are -1.
                RaiseEvent ContextMenu(Handled, -1, -1)
            End If
            If Handled = True Then Exit Function
        End If
    
...
End Select
...
End Sub
Also, as I mentioned before, the context-menu-key on the keyboard works fine.