Const MF_DELETE = &H200&
Const SC_CLOSE = &HF060
Const SC_MAXIMIZE = &HF030
Const SC_MINIMIZE = &HF020
Const SC_MOVE = &HF010
Const SC_SIZE = &HF000
Const MF_INSERT = &H0&
 
Private Declare Function GetSystemMenu Lib "user32" (ByVal hwnd As Long, ByVal _
  bRevert As Long) As Long
Private Declare Function RemoveMenu Lib "user32" (ByVal hMenu As Long, ByVal _
nPosition As Long, ByVal wFlags As Long) As Long
 
 
'X-Button inaktiv
RemoveMenu GetSystemMenu(hwnd, 0), SC_CLOSE, MF_DELETE