Help!! need help for VHDL car detect system.

hey guys, i'm new with vhdl and i have to write the following programm, and i need help.

1.To detect number of car.

2.output s is the current number of car.

3.output a is the previous number of car.

4.to load the the previous number of car into the system when an active-low load input is activated.

5.led to light when 64 cars is detected.

I have problem on the load part so i hope u guys can enlighten me. below are some parts i have done. Thanks:)

library ieee;

use ieee.std_logic_1164.all;

use ieee.numeric_std.all;

entity project is

port ( sensor : in std_logic;

reset : in std_logic;

load : in bit;

s : out std_logic_vector (5 downto 0); --current number

a : out std_logic_vector (5 downto 0); -- previous number

led_on : out bit);

end project;

architecture flow of project is

signal count_sig: unsigned (5 downto 0);

begin

process (sensor, reset, load)

begin

if (reset='1') then

count_sig <= "000000";

elsif rising_edge (sensor) then

count_sig <= count_sig+1;

end if;

end process;

s <= std_logic_vector (count_sig);

end flow;