如何使窗体右上角的"X"无效？

    要Disable Form "X" -->Close的功能(便暗灰色),事实上便是从Form左上方的SystemMenu将关闭的MenuItem去除掉便可以了,去除后,又该如何,那便是在将关闭(Close)的MenuItem加回去 但这里有个小问题,加回去之后"X"仍是暗灰色,要等到我们做了某些固定的动作之后(如TittleBar上Click一下,或选一下SystemMenu等), 我不知道让TittleBar上的这些东西Refresh要送什么消息,所以现在我暂且Send一个在TittleBar上按下Mouse左键的消息给窗体,令"X"能出现的Enable颜色
在窗体上放置一个Command Button,输入以下代码,运行,点击一下Command Button 就可使"X" Enable.
Private Declare Function GetSystemMenu Lib "User32" (ByVal hwnd As Long, ByVal bRevert As Long) As Long
Private Declare Function DeleteMenu Lib "User32" (ByVal hMenu As Long, ByVal nPosition As Long, ByVal wFlags As Long) As Long
Private Declare Function AppendMenu Lib "User32" Alias "AppendMenuA" (ByVal hMenu As Long, ByVal wFlags As Long, ByVal wIDNewItem As Long, ByVal lpNewItem As Any) As Long
Private Declare Function GetMenuString Lib "User32" Alias "GetMenuStringA" (ByVal hMenu As Long, ByVal wIDItem As Long, ByVal lpString As String, ByVal nMaxCount As Long, ByVal wFlag As Long) As Long
Private Declare Function SendMessage Lib "User32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long
Const WM_NCLBUTTONDBLCLK = &HA3
Const WM_NCLBUTTONDOWN = &HA1
Const HTCAPTION = 2
Const MF_STRING = &H0&
Const MF_BYCOMMAND = &H0&
Const SC_CLOSE = &HF060
Private hMenu As Long
Private CloseStr As String ''纪录Close MenuItem的字符串
Private Sub Command1_Click()
''将"关闭"的那个MenuItem重新加入
Call AppendMenu(hMenu, MF_STRING, SC_CLOSE, CloseStr)
''令"X"出现Enable的颜色
Call SendMessage(hwnd, WM_NCLBUTTONDOWN, HTCAPTION, 0&)
End Sub
Private Sub Form_Load()
hMenu = GetSystemMenu(Me.hwnd, 0)
CloseStr = String(255, 0)
''SC_CLOSE即是"关闭"的MenuItem ID
Call GetMenuString(hMenu, SC_CLOSE, CloseStr, 256, MF_BYCOMMAND)
CloseStr = Left(CloseStr, InStr(1, CloseStr, Chr(0)) - 1)
Call DeleteMenu(hMenu, SC_CLOSE, MF_BYCOMMAND)
End Sub