MDI親フォームのToolBarを切り替えるには？

		private void FormABC_Load(object sender, System.EventArgs e)
		{
			toolBarA.Visible = false;
			toolBarB.Visible = false;
			toolBarC.Visible = false;

			ShowFormA();
			ShowFormB();
			ShowFormC();

			// この２行を追加
　　　　　　　　　　　　   frmC.WindowState = FormWindowState.Minimized;
			frmC.Hide();
		}

		private void FormA_Closing(object sender, System.ComponentModel.CancelEventArgs e)
		{
			e.Cancel = true;
			this.WindowState = System.Windows.Forms.FormWindowState.Normal;	// この行を追加	
			Hide();
		}

Public Interface IhaveToolbar
    ReadOnly Property ToolBar() As ToolBar
End Interface

    Implements IhaveToolbar
    Public ReadOnly Property ToolBar() As System.Windows.Forms.ToolBar Implements IhaveToolbar.ToolBar
        Get
            ToolBar = ToolBar1
        End Get
    End Property

    Private WithEvents formA As formA
    Private WithEvents formB As formB
    Private WithEvents formC As formC

    Private _MdiChildren As New System.Collections.ArrayList
    Private _curForm As Form

    Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.Load
        formA = New formA
        formA.MdiParent = Me
        formA.Text = "A"
        formA.Show()
        _MdiChildren.Add(formA)

        formB = New formB
        formB.MdiParent = Me
        formB.Text = "B"
        formB.Show()
        _MdiChildren.Add(formB)

        formC = New formC
        formC.MdiParent = Me
        formC.Text = "C"
        formC.Show()
        _MdiChildren.Add(formC)

    End Sub


    Private Sub Form1_MdiChildActivate(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.MdiChildActivate

        'ToolBarの処理
        SuspendLayout()
        If Not _curForm Is Nothing Then
            If TypeOf _curForm Is IhaveToolbar Then
                CType(_curForm, IhaveToolbar).ToolBar.Parent = Nothing
            End If
        End If
        _curForm = Me.ActiveMdiChild
        If Not _curForm Is Nothing Then
            If TypeOf _curForm Is IhaveToolbar Then
                CType(_curForm, IhaveToolbar).ToolBar.Parent = Panel3
            End If
        End If
        ResumeLayout()

    End Sub


    Dim _forceClose As Boolean = False
    Private Sub MdiChild_Closing(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles formA.Closing, formB.Closing, formC.Closing
        If _forceClose Then Exit Sub

        Dim form As Form = sender
        form.Hide()
        e.Cancel = True
    End Sub

    Private Sub Form1_Closing(ByVal sender As Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles MyBase.Closing
        _forceClose = True
        For Each child As Form In _MdiChildren
            If TypeOf child Is IhaveToolbar Then
                CType(child, IhaveToolbar).ToolBar.Parent = child
            End If
            child.Hide()
        Next
        e.Cancel = False
    End Sub

    Private Sub ToolBar1_ButtonClick(ByVal sender As System.Object, ByVal e As System.Windows.Forms.ToolBarButtonClickEventArgs) Handles ToolBar1.ButtonClick
        Dim form As Form = _MdiChildren(ToolBar1.Buttons.IndexOf(e.Button))
        form.Show()
        form.Activate()

    End Sub