Start and end times of the stream can be received from the .ASX metafile. You may use them in NetXFer as described in our FAQ:
How to record streaming media file in parts: Start and end times of a streaming media

However it is much easier to record such streams with WM Recorder in AUTO recording mode (PRO or ADA). You just start WM Recorder in the AUTO recording mode and it records every Windows Media stream your Windows Media Player plays. You don't have to worry about stream URLs, start and end times of the stream, stream authentication,...