switching problem

Hello!

I'm trying to build the following thing: a 7-segment-led that increases its
value every time a switch is pressed.

library IEEE;
use IEEE.STD_LOGIC_1164.ALL;
use IEEE.STD_LOGIC_ARITH.ALL;
use IEEE.STD_LOGIC_UNSIGNED.ALL;

entity sevsegment is
    Port (
    clk_i: in std_logic;
    sevseg : out std_logic_vector(6 downto 0);
           reset : in std_logic;
     switch: in std_logic);
end sevsegment;

architecture Behavioral of sevsegment is
signal sevseg_s: std_logic_vector(6 downto 0);
begin

process(reset,switch,clk_i)
variable counter: integer range 0 to 9;
begin
 if clk_i'event and clk_i='1' then
   if reset='0' then
        counter:=0;
        sevseg_s <= "1111110";
  elsif switch'event and switch='0' then
      if counter<9 then
           counter:=counter+1;
      else
           counter:=0;
      end if;
  case counter is
   when 0 => sevseg_s <= "1111110";
   when 1 => sevseg_s <= "0110000";
   when 2 => sevseg_s <= "1101101";
   when 3 => sevseg_s <= "1111001";
   when 4 => sevseg_s <= "0110011";
   when 5 => sevseg_s <= "1011011";
   when 6 => sevseg_s <= "1011111";
   when 7 => sevseg_s <= "1110000";
   when 8 => sevseg_s <= "1111111";
   when 9 => sevseg_s <= "1111011";
  end case;
end if;
end process;

sevseg <= sevseg_s;

end Behavioral;


Why doesn't it work? I know that "multiple clocks" are not allowed, but i
can't find any solution to solve my problem.... :-(((((((((
In the end, everything should be implemented to a spartanII-FPGA...

Thank you very much,
Simone