well I'd guess they key to that is not to store the rating for a series of games in a table.
if you identify the date the game was played (and you have) you should design an algolryhtm which calculates the rating based on a date interval.
If you have to store the rating, for performance or other reasons then logically I'd expect to store the rating for this game (and preceeding games), not rating for previous games in this game.
once you have decided on your algolrhtym convert that into a query
select (<mycomplexratingmathmaticalfunction>) as Rating from <mytable> where gameplayedon between (#startdate# and #enddate#) where teamid=<blah>
you then need to associate that with the parent SQL I forget what the sub query syntax is.. truth be told, I only recently found that Access supported sub queries thanks to this forum and I've never really used them enough to sink in.
I still don't think its right to store this as its derived data. However I think you could argue that you needed to know the teams ratings going into a game for each game they've played, if you need that available for each and every game (ie seattle were n% after game1, o% after game2, z% after game13. It sounds all "too American" sports to me.