one way would be to just index all players and their stats at the end of the map/round..
then at the end of the next round.. their rounds "stat" is just the difference between the end of that round and the end of the previous round...
if you need some help let me know (i've been out of the battlefront loop for quite a while)..
i actually am working right now on my BF1942 league stat dealy.
its still a work in progress..