new GateObject;
new bool:GateObject;

forward GateCheck();

GM init or whatever:
SetTimer("GateCheck", 500, 1);

public GateCheck()
{
	if(!IsObjectMoving(GateObject))
	{
		for(new i = 0, j = GetPlayerPoolSize(); i <= j; i++)
		{
			if(IsPlayerInRangeOfPoint(i, Distance, X, Y, Z))
			{
				if(GateObject == false)
				{
					MoveObject(GateObject, X, Y, Z, SPEED, Xrot, Yrot, Zrot); // close
					GateObject = true;
				}
			}
			else if(GateObject == true)
			{
				MoveObject(GateObject, X, Y, Z, SPEED, Xrot, Yrot, Zrot); // open
				GateObject = false;
			}
		}
	}
	return 1;
}

COMMAND:gate(playerid, params[])
{
	MoveObject(GateObject, X, Y, Z, SPEED, Xrot, Yrot, Zrot); // close
	Gate = false;
	return 1;
}