#define MAX_LEVEL  25    //on top

if(Exp[playerid]>=MAX_LEVEL)return 1;//supposing you save player experience in variable Exp[playerid]
//place this line in function or timer or stock where ever you update player's experience

if(PlayerInfo[playerid][pLevel]==25)
{
  //you code here...(Stop the timer or whatever you have you level/experience)
}

public UpdateExp(playerid)
{
        new string[30]; // String.
        if(IsPlayerConnected(playerid) == 1) // Checks if player is connected.
        {
            //new points[248]; // Points.
            new nxtlevel = PlayerInfo[playerid][pLevel]+1; // As soon as its executed, It adds +1 to your score.
            new expamount = nxtlevel*levelexp+100; // Exp amount, Its 2 CURRENTLY but you can raise it by adding +number after levelexp
           // new pfile[100];
            if(PlayerInfo[playerid][pExp] < expamount) // Checks if player's exp amount is above the required one or not.
            {
                //format(points,sizeof(points)," You need [%d] Exp Points in order to level up, You currently have [%d]",expamount,PlayerInfo[playerid][pExp]); // Format, This is pretty obvious.
                //SendClientMessage(playerid,white,points); // Sends the message.
                return 1;
            }
            else
            {
                PlayerInfo[playerid][pExp] = 0; //  Sets the EXP amount to 0 as you level'd up.
                PlayerInfo[playerid][pLevel]++; // Adds a level.
                format(string,sizeof(string),"~g~Your now level:[%d] dan mendapatkan $%d",PlayerInfo[playerid][pLevel], CashForLevelUp * PlayerInfo[playerid][pLevel] * CashMultiplier); // Format.
                GameTextForPlayer(playerid,string,3000,4); // Sends gametext about his new level'ing up.
                GivePlayerMoney(playerid, CashForLevelUp * PlayerInfo[playerid][pLevel] * CashMultiplier);
                return 1;
            }
        }
        return 1;
    }

#define MAX_LEVEL 25 //on top


public UpdateExp(playerid)
{
        new string[30]; // String.
        if(IsPlayerConnected(playerid) == 1) // Checks if player is connected.
        {
          if(PlayerInfo[playerid][pLevel]>=MAX_LEVEL)return SendClientMessage(playerid,-1,"{ff0000}Max Level Reached can level up more.");//ADDED THIS LINE
            //new points[248]; // Points.
            new nxtlevel = PlayerInfo[playerid][pLevel]+1; // As soon as its executed, It adds +1 to your score.
            new expamount = nxtlevel*levelexp+100; // Exp amount, Its 2 CURRENTLY but you can raise it by adding +number after levelexp
           // new pfile[100];
            if(PlayerInfo[playerid][pExp] < expamount) // Checks if player's exp amount is above the required one or not.
            {
                //format(points,sizeof(points)," You need [%d] Exp Points in order to level up, You currently have [%d]",expamount,PlayerInfo[playerid][pExp]); // Format, This is pretty obvious.
                //SendClientMessage(playerid,white,points); // Sends the message.
                return 1;
            }
            else
            {
                PlayerInfo[playerid][pExp] = 0; //  Sets the EXP amount to 0 as you level'd up.
                PlayerInfo[playerid][pLevel]++; // Adds a level.
                format(string,sizeof(string),"~g~Your now level:[%d] dan mendapatkan $%d",PlayerInfo[playerid][pLevel], CashForLevelUp * PlayerInfo[playerid][pLevel] * CashMultiplier); // Format.
                GameTextForPlayer(playerid,string,3000,4); // Sends gametext about his new level'ing up.
                GivePlayerMoney(playerid, CashForLevelUp * PlayerInfo[playerid][pLevel] * CashMultiplier);
                return 1;
            }
        }
        return 1;
    }