[SilentSoul]

pawn Код:

CMD:loadtrailer(playerid, params[])
{   
    new vehicleid;
    if(!IsPlayerInRangeOfPoint(playerid, 10, -168.2511, -286.3422, 2.3614)) return SendClientMessage(playerid, -1, "You are not at the loading point.");
    {
        if(GetVehicleModel(vehicleid) == 584)
        {
            ShowPlayerDialog(playerid, DIALOG_FUEL_TRAILER, DIALOG_STYLE_INPUT, "Fuel Stations", "Broadway  /n", "Deliver", "Cancel");
        }
        else return SendClientMessage(playerid, COLOR_RED, "You do not have a trailer attached!");
    }
    return 1;
}

EDIT: Ops , sorry i didn't read the thread correctly , to check if the player inside trailer you can use GetVehicleModel