Code:
Friend WithEvents ContentsToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents HelpMenu As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents IndexToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents SearchToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents ToolStripSeparator8 As System.Windows.Forms.ToolStripSeparator
    Friend WithEvents AboutToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents ArrangeIconsToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents CloseAllToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents NewWindowToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents WindowsMenu As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents CascadeToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents TileVerticalToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents TileHorizontalToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents OptionsToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents HelpToolStripButton As System.Windows.Forms.ToolStripButton
    Friend WithEvents ToolStripSeparator2 As System.Windows.Forms.ToolStripSeparator
    Friend WithEvents PrintPreviewToolStripButton As System.Windows.Forms.ToolStripButton
    Friend WithEvents ToolTip As System.Windows.Forms.ToolTip
    Friend WithEvents ToolStripStatusLabel As System.Windows.Forms.ToolStripStatusLabel
    Friend WithEvents StatusStrip As System.Windows.Forms.StatusStrip
    Friend WithEvents PrintToolStripButton As System.Windows.Forms.ToolStripButton
    Friend WithEvents NewToolStripButton As System.Windows.Forms.ToolStripButton
    Friend WithEvents ToolStrip As System.Windows.Forms.ToolStrip
    Friend WithEvents OpenToolStripButton As System.Windows.Forms.ToolStripButton
    Friend WithEvents SaveToolStripButton As System.Windows.Forms.ToolStripButton
    Friend WithEvents ToolStripSeparator1 As System.Windows.Forms.ToolStripSeparator
    Friend WithEvents PrintPreviewToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents PrintToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents ToolStripSeparator4 As System.Windows.Forms.ToolStripSeparator
    Friend WithEvents ExitToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents ToolStripSeparator5 As System.Windows.Forms.ToolStripSeparator
    Friend WithEvents PrintSetupToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents SaveAsToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents NewToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents FileMenu As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents OpenToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents ToolStripSeparator3 As System.Windows.Forms.ToolStripSeparator
    Friend WithEvents SaveToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents MenuStrip As System.Windows.Forms.MenuStrip
    Friend WithEvents EditMenu As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents UndoToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents RedoToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents ToolStripSeparator6 As System.Windows.Forms.ToolStripSeparator
    Friend WithEvents CutToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents CopyToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents PasteToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents ToolStripSeparator7 As System.Windows.Forms.ToolStripSeparator
    Friend WithEvents SelectAllToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents ViewMenu As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents ToolBarToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents StatusBarToolStripMenuItem As System.Windows.Forms.ToolStripMenuItem
    Friend WithEvents ToolsMenu As System.Windows.Forms.ToolStripMenuItem
End Class

MsgBoxForeGround :

Code:
' Force MsgBox to ForeGround & TopMost v1.02
' A workaround for when msgbox hides behind other windows.
'
' Usage:
' 1) Add this module to your project.
' 2) Replace "MessageBox.Show" with "MessageBoxEx" where needed.

Imports System.Runtime.InteropServices
Module MsgBoxForeGround
    Private WithEvents msgTimer As New Timer
    Private msgCaption As String

    <DllImport("user32.dll", CharSet:=CharSet.Auto, SetLastError:=True)>
    Private Function SetForegroundWindow(ByVal hWnd As IntPtr) As Boolean
    End Function

    <DllImport("user32.dll", CharSet:=CharSet.Auto, EntryPoint:="FindWindow")> _
    Private Function FindWindow(ByVal lpClassName As String, ByVal lpWindowName As String) As IntPtr
    End Function

    Private Const SWP_NOMOVE As UInteger = &H2
    Private Const SWP_NOSIZE As UInteger = &H1
    Private Const SWP_SHOWWINDOW As UInteger = &H40
    Private ReadOnly HWND_TOPMOST As New IntPtr(-1)
    <DllImport("user32.dll", EntryPoint:="SetWindowPos")> _
    Private Function SetWindowPos(ByVal hWnd As IntPtr, ByVal hWndInsertAfter As IntPtr, ByVal X As Integer, ByVal Y As Integer, ByVal cx As Integer, ByVal cy As Integer, ByVal uFlags As UInteger) As Boolean
    End Function

    Private Sub msgTimer_Tick(sender As Object, e As System.EventArgs) Handles msgTimer.Tick
        ' get handle to msgbox
        Dim hWnd As IntPtr = FindWindow("#32770", msgCaption)
        If Not hWnd.Equals(IntPtr.Zero) Then
            ' stop timer
            msgTimer.Stop()
            ' set msgbox topmost
            SetWindowPos(hWnd, HWND_TOPMOST, 0, 0, 0, 0, SWP_NOMOVE Or SWP_NOSIZE Or SWP_SHOWWINDOW)
            ' set msgbox foreground
            SetForegroundWindow(hWnd)
        End If
    End Sub

    ' // show message box & return dialog result //
    Public Function MessageBoxEx(ByVal text As String _
            , Optional ByVal caption As String = "" _
            , Optional ByVal buttons As MessageBoxButtons = MessageBoxButtons.OK _
            , Optional ByVal icon As MessageBoxIcon = MessageBoxIcon.None _
            , Optional ByVal defaultButton As MessageBoxDefaultButton = MessageBoxDefaultButton.Button1) _
              As DialogResult

        msgCaption = caption 'msgbox titlebar text
        msgTimer.Interval = 30 ' timer speed
        msgTimer.Start() ' start timer
        ' show our msgbox
        Dim result As DialogResult = MessageBox.Show(text, caption, buttons, icon, defaultButton)
        msgTimer.Stop() ' make sure timer has stopped!
        msgTimer.Dispose()
        Return result ' return msgbox result.
    End Function
End Module
This is all my code in the project.

1 - For the test, create some new form1 by press Fichier -> Nouveau

2 - Then press Fenêtre -> Fermer tout

When you will press "Fermer Tout" all Child Form will be close.

Thx for your help

BTw : Sorry my windows is in french.