Node click doesn't care what button you clicked with. What you can do is to use a MouseDown event to check if the user clicked with the right mouse button.
Code:
Private Sub TreeView1_MouseDown(Button As Integer, Shift As Integer, x As Single, y As Single)
    Dim nodCurrent As Node
    
    If Button = vbRightButton Then
        Set nodCurrent = TreeView1.HitTest(x, y)
        If Not nodCurrent Is Nothing Then
            nodCurrent.Selected = True
            MsgBox "You right clicked on " & nodCurrent.Text
        End If
    End If
End Sub