[Iuri]

Okay so it works kinda simple. First, you make a new variable for all the players and a normal variable( e.g:

pawn Код:

new Challenger[MAX_PLAYERS] = INVALID_PLAYER_ID;
new RaceLeader = INVALID_PLAYER_ID;

, then a command to invite someone to race.Do

pawn Код:

Challenger[playerid] = giveplayerid;
Challenger[giveplayerid] = playerid;

when the command is executed.
In case if the opponent accepts, just set a timer for a countdown. If he refuses, add:

pawn Код:

Challenger[Challenger[playerid]] = INVALID_PLAYER_ID;
Challenger[playerid] = INVALID_PLAYER_ID;

Now let's go to the lead...

pawn Код:

new Float: Distance = GetDistanceBetweenPlayers(Challenger[playerid],playerid);
if(Distance > Float:Distance)
{
     RaceLeader = Challenger[playerid];
     new string[56],pName[MAX_PLAYER_NAME];
     GetPlayerName(Challenger[playerid],pName,sizeof(pName));
     format(string,sizeof(string)," %s is in the lead.",pName));
     SendClientMessage(playerid,colour,string);
     SendClientMessage(Challenger[playerid],colour," You are in the lead.");
}
else if(Distance < Float:Distance)
{
     RaceLeader = playerid;
     new string[56],pName[MAX_PLAYER_NAME];
     GetPlayerName(playerid,pName,sizeof(pName));
     format(string,sizeof(string)," %s is in the lead.",pName));
     SendClientMessage(Challenger[playerid],colour,string);
     SendClientMessage(colour,playerid," You are in the lead.");
}

Just be sure to change the Float: Distance and the colour, and to set an INVALID_PLAYER_ID for all the new created variables.