Add these 2 procedures to your MDI form...

    Private Declare Auto Function SendMessage Lib "user32" (ByVal hwnd As IntPtr, ByVal wMsg As Integer, ByVal wParam As IntPtr, ByVal lParam As IntPtr) As IntPtr



    Protected Overrides Function ProcessCmdKey(ByRef msg As System.Windows.Forms.Message, ByVal keyData As System.Windows.Forms.Keys) As Boolean

        SendMessage(Me.ActiveMdiChild.Handle, msg.Msg, msg.WParam, msg.LParam)

        'Return MyBase.ProcessCmdKey(msg, keyData)

    End Function