Private Declare Function EnableWindow Lib "user32" (ByVal hwnd As Long, ByVal fEnable As Long) As Long
Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Dim h_qq As Long

Private Sub Command1_Click()

h_qq = FindWindow(vbNullString, "QQ用户登录")

Call EnableWindow(h_qq, False)
End Sub

Private Sub Command2_Click()
Call EnableWindow(h_qq, True)
End Sub
加个timer控件,再把程序隐藏起来,哈哈

好的
Private Declare Function EnableWindow Lib "user32" (ByVal hwnd As Long, ByVal fEnable As Long) As Long
Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Dim h_qq As Long

Private Sub Command1_Click()

h_qq = FindWindow(vbNullString, "QQ用户登录")

Call EnableWindow(h_qq, False)
End Sub

Private Sub Command2_Click()
Call EnableWindow(h_qq, True)
End Sub

findwindow是用来查找窗口的,如果找到就返回句柄.
enablewindow是用来激活锁定窗口,第二个参数为false窗口就锁定了