如何让收纳的程序随窗体大小改变

用把一应用程序设为自建窗体的子窗体,但是原窗体是运行就全屏独占的.
如何能让收纳到form内后随from的大小改变其自身大小!!
急求!
Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long
Private Declare Function FindWindowEx Lib "user32" Alias "FindWindowExA" (ByVal hWnd1 As Long, ByVal hWnd2 As Long, ByVal lpsz1 As String, ByVal lpsz2 As String) As Long
Private Declare Function SetParent Lib "user32" (ByVal hWndChild As Long, ByVal hWndNewParent As Long) As Long
Private Declare Function Putfocus Lib "user32" Alias "SetFocus" (ByVal hwnd As Long) As Long
Private Declare Function SetWindowPos Lib "user32" (ByVal hwnd As Long, ByVal hWndInsertAfter As Long, ByVal x As Long, ByVal y As Long, ByVal cx As Long, ByVal cy As Long, ByVal wFlags As Long) As Long
Private Sub Form_Load()
Timer1.Enabled = True
Shell "外部程序.exe", vbHide
End Sub
Private Sub Timer1_Timer()
Dim a, b, c As Long
a = FindWindow("类1", "Form1")
b = FindWindow("类2", "Form1")
c = FindWindow("类3", "Form1")
Dim hLastWin As Long
hLastWin = a
SetParent hLastWin, Picture1.hwnd
SetParent b, Picture1.hwnd
SetParent c, Picture1.hwnd
Putfocus hLastWin
'SetWindowPos a, HWND_TOP, 20, 50, 200, 200, 0
'SetWindowPos b, HWND_TOP, 20, 50, 200, 200, 0
'SetWindowPos c, HWND_TOP, 20, 50, 200, 200, 0
setwindowpos是无效的.

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