TabIndex - dotNet controls and native controls

Here is the code below where I have two native buttons and two dotNet controls.

When you open this dialog up pressing tab should cycle through each button but it doesn't as they're two different types.

Is there a way around this? To even get the dotNet controls working would be a start.

try destroydialog dialog catch()

rollout dialog "Tab Index" width:200 height:100
(

  checkbutton show_bt "Button 1"  width:100 height:20 align:#center
  checkbutton btn_shift "Button 2"  width:100 height:20 align:#center

  dotnetcontrol btn1 "Button" text:"Button 3" width:100 height:20 align:#center
  dotnetcontrol btn2 "Button" text:"Button 4" width:100 height:20 align:#center

  on dialog open do
  (

    btn1.FlatStyle = btn1.FlatStyle.System
    btn2.FlatStyle = btn2.FlatStyle.System

    -- How can I set up tab index when using max buttons and dotNet buttons?
    -- I want to cycle through them all inc. the native buttons when pressing
    -- the tab key.
    btn1.TabIndex = 0
    btn2.TabIndex = 1

    setFocus btn2

    )
  )
createdialog dialog

TabIndex not working on a dotNet form either.

(
  fn pressingSituation_fn a b =
  (
    format "TabIndex value: %\n" a.TabIndex
    )
  -- Create a DotNet Button
  mButton1 = dotNetObject "System.Windows.Forms.Button"
  mButton1.text = "BIG DotNet Button 1"
  mButton1.size = dotNetObject "System.Drawing.Size" 100 100
  mButton1.location = dotNetObject "System.Drawing.Point" 0 0

  -- Create a DotNet Button
  mButton2 = dotNetObject "System.Windows.Forms.Button"
  mButton2.text = "BIG DotNet Button 2"
  mButton2.size = dotNetObject "System.Drawing.Size" 100 100
  mButton2.location = dotNetObject "System.Drawing.Point" 100 100

  -- TabIndex
  mButton1.TabIndex = 0
  mButton2.TabIndex = 1

  -- Create a DotNet Form
  hForm = dotNetObject "System.Windows.Forms.Form"
  hForm.size = dotNetObject "System.Drawing.Size" 215 238
  hForm.controls.add mButton1 -- Add the Button to the Form
  hForm.controls.add mButton2 -- Add the Button to the Form
  hForm.topmost = true
  -- Add an Event Handler for the click event:
  dotNet.addEventHandler mButton1 "click" pressingSituation_fn
  dotNet.addEventHandler mButton2 "click" pressingSituation_fn
  hForm.show() -- Show the Form with the Button
  )