VB 在我的窗口内，运行外部程序

Option Explicit
Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As Long, ByVal lpWindowName As Long) As Long
Private Declare Function GetParent Lib "user32" (ByVal hwnd As Long) As Long
Private Declare Function SetParent Lib "user32" (ByVal hWndChild As Long, ByVal hWndNewParent As Long) As Long
Private Declare Function GetWindowThreadProcessId Lib "user32" (ByVal hwnd As Long, lpdwProcessId As Long) As Long
Private Declare Function GetWindow Lib "user32" (ByVal hwnd As Long, ByVal wCmd As Long) As Long
Private Declare Function LockWindowUpdate Lib "user32" (ByVal hwndLock As Long) As Long
Private Declare Function GetDesktopWindow Lib "user32" () As Long
Private Declare Function DestroyWindow Lib "user32" (ByVal hwnd As Long) As Long
Private Declare Function TerminateProcess Lib "kernel32" (ByVal hProcess As Long, ByVal uExitCode As Long) As Long
Private Declare Function GetCurrentProcess Lib "kernel32" () As Long
Private Declare Function Putfocus Lib "user32" Alias "SetFocus" (ByVal hwnd As Long) As Long

Private Const GW_HWNDNEXT = 2
Private m_Hwnd As Long

Private Sub Form_Load()
    Dim dblPid As Long
    Call LockWindowUpdate(GetDesktopWindow)
    dblPid = Shell("c:\windows\notepad.exe", vbNormalFocus)
    m_Hwnd = InstanceToWnd(dblPid) '根据进程PID找窗口句柄
    SetParent m_Hwnd, Me.hwnd
    Putfocus m_Hwnd                 '记事本设置焦点
    Call LockWindowUpdate(0)
End Sub

Function InstanceToWnd(ByVal target_pid As Long) As Long
    Dim i As Long, lHwnd As Long, lPid As Long, lThreadId As Long
    lHwnd = FindWindow(ByVal 0&, ByVal 0&)   '查找第一个窗口
    Do While lHwnd <> 0
        i = i + 1
        If i Mod 20 = 0 Then DoEvents
        '判断窗口是否没父窗口
        If GetParent(lHwnd) = 0 Then
            '获取该窗口的线程ID
            lThreadId = GetWindowThreadProcessId(lHwnd, lPid)
            If lPid = target_pid Then '找到PID所在窗口句柄
                InstanceToWnd = lHwnd
                Exit Do
            End If
        End If
        '继续查找下一个兄弟窗口
        lHwnd = GetWindow(lHwnd, GW_HWNDNEXT)
        Debug.Print Hex$(lHwnd)
    Loop
End Function

Private Sub Form_Unload(Cancel As Integer)
    Call DestroyWindow(m_Hwnd)
    'TerminateProcess GetCurrentProcess, 0    '野蛮了些
    Set Form1 = Nothing
End Sub