Use a switch/case statement.
pawn Код:
switch(PlayerInfo[playerid][Xp])
{
case 20:
{
SendClientMessage(playerid, COLOR_GREEN, "You have been promoted to Private I!");
}
case 40:
{
SendClientMessage(playerid, COLOR_GREEN, "You have been promoted to Private II!");
}
//etc.
}
And I recommend not using any timers for that, just call the function whenever the score increases.