[iPrivate]

You mean something like this:

pawn Код:

stock random(min, max)
{    

    new randomtext = random(max-min)+min;    
    return randomtext;
}

And then you could use it:

pawn Код:

CMD:refuel(playerid, params[])
{
     new string[126];
     format(string, sizeof(string), "You have refueled your vehicle with %d liters of fuel.", random(50,100));
     SendClientMessage(playerid, 0xFFFFFFFF, string);
     return 1;
}

I think that's what you're asking. Change the command part on your needs, just see the example of using the stock.