Visual Basic: Desabilitar Botão Fechar (X) do MDIForm

Código para desabilitar o botão fechar de um MDI Form em visual basic:



Em um módulo, coloca-se:

'Para desabilitar o botão Fechar

    Public Declare Function DeleteMenu Lib "user32" (ByVal HMenu As Long, ByVal nPosition As Long, ByVal wFlags As Long) As Long
    Public Declare Function GetSystemMenu Lib "user32" (ByVal hwnd As Long, ByVal bRevert As Long) As Long
    Public Const MF_BYPOSITION = &H400&

No Load do Formulário coloca-se:
   
Dim HMenu as Long

 'Desabilita Botão Fechar

    HMenu = GetSystemMenu(hwnd, False)
    DeleteMenu HMenu, 6, MF_BYPOSITION