Kind of error-handler in a pgsql function

Hi,

When I write in psql:
testdb=# update table1 set tableattribute='any' where table_nr=1;
if a tuple exists, I get this message
testdb=# update 1
if no tuple with table_nr=1 exists, I get this message
testdb=# update 0

Is there a possibility to make a difference in a pgsql function like this:
create function updTable(text,integer) returns int AS
'DECLARE
msg ALIAS FOR $1;
nr ALIAS FOR $2;
BEGIN
update table1 set tableattribute=msg where table_nr=nr;
--pseudocode
if update = 0 then
return 0;
else
return 1;
end if;
END;
'language 'plpgsql';

or for a function, which inserts data:
create function insTable(text,integer) returns int AS
'DECLARE
msg ALIAS FOR $1;
nr ALIAS FOR $2;
BEGIN
insert into table1 values (nr,msg);
--pseudocode
if error= cannot insert duplicate key.....then
return 0;
else
return 1;
end if;
END;
'language 'plpgsql';

I want to know the result of an insert or update, because I call these functions from an Access form and the next steps of the program depend on these results.

I hope, someone can help me, because I didn't find anything in the docu or mailing list.
Thanks in advance
Irina

E-Mail: i(dot)hasenoehrl(at)aon(dot)at