This info is for Addin development hope its useful even if it's a little bit late.
Public Sub Active()
m_FileUIEvents = m_inventorApplication.FileUIEvents
' replace meventsobj by the inventor
AddHandler m_inventorApplication.FileUIEvents.OnPopulateFileMetadata, AddressOf m_fileUIEvents_OnPopulateFileMetadata
Public Sub m_fileUIEvents_OnPopulateFileMetadata(ByVal FileMetadataObjects As Inventor.ObjectsEnumerator, ByVal Formulae As String, ByVal Context As Inventor.NameValueMap, ByRef HandlingCode As Inventor.HandlingCodeEnum) Handles m_FileUIEvents.OnPopulateFileMetadata
HandlingCode = HandlingCodeEnum.kEventHandled
MsgBox("Testing 1 2 3")
Dim oMetaData As FileMetadata
If FileMetadataObjects.Count > 0 Then
For Each oMetaData In FileMetadataObjects
'suggest custom name
oMetaData.FileName = "asdk_" & oMetaData.FileName
oMetaData.FileNameOverridden = True
Next oMetaData
'tell Inventor the event is handled
HandlingCode = HandlingCodeEnum.kEventHandled
End If
End Sub
https://spiderinnet2.typepad.com/blog/2013/03/inventor-api-vbnet-fileui-events.html