Well. If you load 4k xp and then play a game for 500xp, and finish it or die, it will automatically create a name-bound code for 4,5k xp in the savecode.txt. You can copey and paste it at start of a new youtd-game, to load this xp. If u want to leave or got lag-issues u can also type "-save" to create a code. The code is different on every single xp you got. (xp=gamescore/1000).
I think on ent.connect you can also let the program do all this on its own, but im not sure, since i dont use it

If you want to learn something about you-td look at this:
http://www.eeve.org/ or ask me if you want

(lvl 67) im online kinda everyday (ingame:
guennter@useast.battle.net)
it needs some time to learn how the map works, but then u just have to admit, its AWESOME
Gunther and the Sunshine-Girls. Hell Yeah