I have a problem using :!value in special validation with PLSQL block

When I try to use user input with the :!value argument in a date field, it always returns the value "A00".
The code I use for special validation is:

FND PLSQL " DECLARE


v_value varchar2( 11 ) := :!value ;

BEGIN


if v_value >=sysdate then

fnd_message.set_name('FND','FND_GENERIC_MESSAGE' );

fnd_message.set_token('MESSAGE','TEST');


fnd_message.raise_error;


end if;


END; "