FAQ's de VB6

[GeoAvila]

Pregunta:
Como bloquear el botton de cerrar de un formulario?

Respuesta:
ok bueno aqui va la respuesta..

coloca esto en tu form

Código:

Private Sub Form_Load()
Bloquear_Cerrar
End Sub
Private Sub Bloquear_Cerrar()
Dim hMenu As Long
    '
hMenu = GetSystemMenu(hWnd, 0)
    ' Deshabilitar el menú cerrar del formulario
Call ModifyMenu(hMenu, SC_CLOSE, MF_BYCOMMAND Or MF_GRAYED, -10, "Close")
End Sub

y en un modulo esto..

Código:

Public Declare Function GetSystemMenu Lib "user32" _
    (ByVal hWnd As Long, ByVal bRevert As Long) As Long
Public Declare Function ModifyMenu Lib "user32" Alias "ModifyMenuA" _
    (ByVal hMenu As Long, ByVal nPosition As Long, _
    ByVal wFlags As Long, ByVal wIDNewItem As Long, _
    ByVal lpString As Any) As Long
Public Declare Function DrawMenuBar Lib "user32" _
    (ByVal hWnd As Long) As Long
'
Public Const MF_BYCOMMAND = &H0&
Public Const MF_ENABLED = &H0&
Public Const MF_GRAYED = &H1&
'
Public Const SC_CLOSE = &HF060&

nos vemos y espero les sirva el codigo...