Sorry but I can not translate that to my code.. 
This code work when I save the part, but i´t wont run when I save the part from idw.
This code in modifyde from: Sheet Metal Extents Add-In
Private Sub m_appEvents_OnSaveDocument(ByVal DocumentObject As Inventor._Document, ByVal BeforeOrAfter As Inventor.EventTimingEnum, ByVal Context As Inventor.NameValueMap, ByRef HandlingCode As Inventor.HandlingCodeEnum) Handles m_appEvents.OnSaveDocument
If BeforeOrAfter = EventTimingEnum.kBefore Then
Dim inventorAppType As Type = System.Type.GetTypeFromProgID("Inventor.Application")
Dim _InvApplication As Inventor.Application = CType(System.Runtime.InteropServices.Marshal.GetActiveObject("Inventor.Application"), Application)
Dim oPartDoc As PartDocument
oPartDoc = CType(_InvApplication.ActiveDocument, Inventor.PartDocument)
' Make sure the document is a sheet metal document.
If oPartDoc.SubType <> "{9C464203-9BAE-11D3-8BAD-0060B0CE6BB4}" Then
MsgBox("A sheet metal document must be open.")
Exit Sub
Else
MsgBox("A sheet metal has been save")
End If
End If
End Sub