[Tamy]

Code:

public OnPlayerUpdate(playerid)
{
    new weapons[14][2];
    for(new i=0; i<13; i++)
   {
       	GetPlayerWeaponData(playerid, i, weapons[i][0], weapons[i][1]);
        if(weapons[i][0] == 24)
        {
            SetPlayerArmedWeapon(playerid, 24);
        }
    }
    return 1;
}

You can also use this code under a timer, OnPlayerUpdate is called more than 50 times in a second.