vb中禁用关闭按钮
Option Explicit

Private Declare Function GetSystemMenu Lib "USER32" (ByVal hwnd As Long, ByVal bRevert As Long) As Long
Private Declare Function GetMenuItemCount Lib "USER32" (ByVal hMenu As Long) As Long
Private Declare Function RemoveMenu Lib "USER32" (ByVal hMenu As Long, ByVal nPosition As Long, ByVal wFlags As Long) As Long
Private Declare Function DrawMenuBar Lib "USER32" (ByVal hwnd As Long) As Long
Private Const MF_BYPOSITION = &H400&
Private Const MF_REMOVE = &H1000&
 
Private Sub DisableX()
         Dim hMenu, nCount, LO     As Long
         hMenu = GetSystemMenu(Me.hwnd, 0)
         nCount = GetMenuItemCount(hMenu)
         LO = RemoveMenu(hMenu, nCount - 1, MF_REMOVE Or MF_BYPOSITION)
         LO = RemoveMenu(hMenu, nCount - 2, MF_REMOVE Or MF_BYPOSITION)
End Sub
 
Private Sub Form_Load()
    Call DisableX
End Sub

出处：https://www.cnblogs.com/topboy168/archive/2006/06/23/433681.html