new Text:bomb;
new timerbomb[MAX_PLAYERS];
forward bombdone(playerid);

public OnPlayerEnterCheckpoint(playerid)
{
    bomb = TextDrawCreate(50.0, 200.0,"Planting a bomb...");
    TextDrawShowForPlayer(playerid, bomb);
    timerbomb[playerid] = SetTimerEx("bombdone", 10000, false, "d", playerid);
    return 1;
}

public OnPlayerLeaveCheckpoint(playerid)
{
    TextDrawHideForPlayer(playerid, bomb); //The person left the checkpoint
    KillTime(timerbomb[playerid]);
    SendClientMessage(playerid,0x00FF00AA,"You left the checkpoint, try again.");
    return 1;
}

public bombdone(playerid)
{
    SendClientMessage(playerid,0x00FF00AA,"You planted succesfull the bomb.");
    TextDrawHideForPlayer(playerid, bomb);
    DisablePlayerCheckpoint(playerid);
    // ... other stuff ... //
    return 1;
}