VHDL HELP!!!!! Kepad decoder code

[mitsui9999]

Help me to solve the problems about the keypad decode.
eg: output: col1 goes high when row1 is high and button press is 1
row 2 is high and button press is 4

i put case or if statements???

let me know that what wrong with it. thanks

entity prog5 is
Port ( reset , clk : in std_logic;
index : in integer range 1 to 12;
col : out std_logic_vector(2 downto 0);
row : in std_logic_vector(3 downto 0));
end prog5;

architecture Behavioral of prog5 is



begin

Process(clk,index)
begin
case col is
when "100" => "1000" <= row; index = 1;
when "100" => "0100" <= row; index = 4;
when "100" => "0010" <= row; index = 7;
end case;

end process ;
end Behavioral;


thanks
Regards
Mitsui9999


mitsui9999