Hi
OT is correct about Betfair not wanting developers to record race data. Even the Betfair data they release is ordered by matched odds to make it difficult to achieve a race replay.
However, it should be easy to set up a trigger which does something trivial (e.g. set a variable) on any selection who's back odds are less than 0. All the horse odds will be recorded with a time stamp in the trigger file (as a failure to match the condition).
Some simple VB software could easily pull the historical data with timestamp from this file.
Just a thought...
Mike