Private Declare Function GetParent Lib "user32" (ByVal hWnd As Long) As Long
Private Declare Function GetWindow Lib "user32" (ByVal hWnd As Long, ByVal wCmd As Long) As Long
Private Declare Function GetWindowThreadProcessId Lib "user32" (ByVal hWnd As Long, lpdwProcessId As Long) As Long
Private Declare Function FindWindow Lib "user32" Alias "FindWindowA" (ByVal lpClassName As String, ByVal lpWindowName As String) As Long

Function InstanceToWnd(ByVal target_pid As Long) As Long
    Dim test_hwnd As Long, test_pid As Long, test_thread_id As Long
    Find the first window
    test_hwnd = FindWindow(ByVal 0&, ByVal 0&)
    Do While test_hwnd <> 0
        Check if the window isnt a child
        If GetParent(test_hwnd) = 0 Then
            Get the windows thread
            test_thread_id = GetWindowThreadProcessId(test_hwnd, test_pid)
            If test_pid = target_pid Then
                InstanceToWnd = test_hwnd
                Exit Do
            End If
        End If       
        test_hwnd = GetWindow(test_hwnd, GW_HWNDNEXT)
    Loop
End Function