Close button Excel 2003 greyed out can't be undone

Using Excel 2003, with below code it should be possible to turn off and on the close button of the Excel application.
Turning off (xapplicatieuit) works just fine; the button gets greyed out, but if I try to turn it on (xapplicatieaan) nothing happens.
Is this typical 2003 or am I doing something wrong?

Option Explicit

Public Declare Function GetSystemMenu Lib "user32" (ByVal hwnd As Long, ByVal bRevert As Long) As Long
Public Declare Function DeleteMenu Lib "user32" (ByVal hMenu As Long, ByVal nPosition As Long, ByVal wFlags As Long) As Long
Declare Function EnableMenuItem Lib "user32" (ByVal hMenu As Long, ByVal uIDEnableItem As Long, ByVal uEnable As Long) As Long
'Used to find the Outlook icon in the system tray. If present then Outlook is running
Private Declare Function FindWindow Lib "user32.dll" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Public Const MF_BYCOMMAND = &H0&
Public Const MF_BYPOSITION = &H400&
Public Const SC_ARRANGE = &HF110
Public Const SC_CLOSE = &HF060
Public Const SC_HOTKEY = &HF150
Public Const SC_HSCROLL = &HF080
Public Const SC_KEYMENU = &HF100
Public Const SC_MAXIMIZE = &HF030
Public Const SC_MINIMIZE = &HF020
Public Const SC_MOVE = &HF010
Public Const SC_NEXTWINDOW = &HF040
Public Const SC_PREVWINDOW = &HF050
Public Const SC_RESTORE = &HF120
Public Const SC_SIZE = &HF000
Public Const SC_VSCROLL = &HF070
Public Const SC_TASKLIST = &HF130
Public Const HWND_TOPMOST = -1
Public Const HWND_NOTOPMOST = -2
Public Const HWND_TOP = 0
Public Const SWP_NOSIZE = &H1
Public Const SWP_NOMOVE = &H2
Public Const GWL_STYLE = (-16)
Sub xapplicatieuit()
' Remove Excel Items
Dim hMenu As Long
hMenu = GetSystemMenu(Application.hwnd, 0)
Call DeleteMenu(hMenu, SC_CLOSE, MF_BYCOMMAND)          ' Disable X (Close) Application button
Call DeleteMenu(hMenu, SC_MINIMIZE, MF_BYCOMMAND)       ' Disable Minimize application button
Call DeleteMenu(hMenu, SC_MAXIMIZE, MF_BYCOMMAND)       ' Disable Maximize application button
End Sub

Sub xapplicatieaan()
' Restore Excel Items
Dim hMenu As Long
hMenu = GetSystemMenu(Application.hwnd, 1)
Call EnableMenuItem(hMenu, SC_CLOSE, MF_BYCOMMAND)      ' Enable X (Close) Application button
Call EnableMenuItem(hMenu, SC_MINIMIZE, MF_BYCOMMAND)   ' Enable Minimize application button
Call EnableMenuItem(hMenu, SC_MAXIMIZE, MF_BYCOMMAND)   ' Enable Maximize application button
End Sub

Anybody any ideas?

Last attempt. Anybody