new bool:HoldingKey[MAX_PLAYERS];
    
public OnPlayerKeyStateChange(playerid, newkeys, oldkeys)
{
    if(newkeys & KEY && !HoldingKey[playerid])
    {
        KeyCheck(playerid);
        HoldingKey[playerid] = true;
    }

    return 1;
}

forward KeyCheck(playerid);
public KeyCheck(playerid)
{
    if(IsPlayerConnected(playerid))
    {
        new
            keys, ud, lr;
            
        GetPlayerKeys(playerid, keys, ud, lr);
        
        if(keys & KEY)
        {
            SetTimerEx("KeyCheck", 100, 0, "i", playerid);
            
            return 0;
        }
    }
    
    HoldingKey[playerid] = false;
    return 0;
}