Private hMdiClient As Long
Private hPrevWin As Long
 
Private Sub MDIForm_Load()
   hMdiClient = FindWindowEx(Me.hwnd, 0, "MDICLIENT", "")
   hPrevWin = SetParent(Picture2.hwnd, hMdiClient)
End Sub
 
Private Sub MDIForm_Resize()
   SetParent Picture2.hwnd, hPrevWin
   SetParent Picture2.hwnd, hMdiClient
End Sub