Well whenever I try that, I just base the xp by amount of kills, and use :
Code:
new frags = get_user_frags(id)
if(frags == x)
{
level2[id] == true
set_user_health(id, get_user_health(id) + 15)
client_print(id, print_chat, "You are level 2, you recieve 15 hp!")
}
Something like that, but if you want a real xp mod you should try to look at the
XP Mod Tutorial by Xuntric
Sorry if my codings a little wrong, it's early and it's just an example.