Forms question ... EXTREMELY URGENT

Question

gurus,
i have the following code in the pl/sql section of the insert button -
declare
p_rate_type dvi.ad_base_rate_types.rate_type%type;
cnt_fnd number;
err_rate_type exception;
begin
** get the rate type
p_rate_type := p_session.get_value_as_VARCHAR2
p_block_name => 'DEFAULT',
p_attribute_name => 'A_RATE_TYPE'
select count(*)
into cnt_fnd
from dvi.ad_base_rate_types
where rate_type = p_rate_type;
if (cnt_fnd > 0) then
raise err_rate_type;
else
doInsert;
end if;
exception
when others then
htp.p('<script language="JavaScript" type="text/javascript">');
htp.p('alert ("Rate Type already exists")');
htp.p('</script>');
raise;
end;
the above code works fine ... i get the alert, but after i click ok of the alert, i get a page with the following -
Error :- undefined exception
after that, when i go to edit the form, i'm not able to open the form.
any ideas ....
thanx a lot ...
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Answer 1

following is the code in the exception section ,
when others then
htp.p('<script language="JavaScript" type="text/javascript">');
htp.p('alert ("Rate Type already exists")');
htp.p('</script>');
raise;
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