function runtime exception

I use db2 9.7.6 full edition for windows. I need develop functions which can be use on sql select expression. Functions must contain modifying sql data and handling runtime exceptions. There are two variants, but I have problems of implementations all requirments in ever variants. The first variant is implementation of sql table function, e.g.

*++CREATE FUNCTION func1 (val CHAR(20))++
++RETURNS table(result varchar(1000))++
++LANGUAGE SQL++
++MODIFIES SQL DATA++
++BEGIN atomic++
++insert into a values(val);++
++ return (select result from a);++
++END++*
It work, but I can't implement handling exception how in sql procedures. When I tried to use block "declare exit handler", I got a syntax errors. The second variant is implementation of pl/sql function, e.g.

*++CREATE OR REPLACE FUNCTION bb++
++RETURN varchar2++
++MODIFIES SQL DATA++
++AS++
++BEGIN++
++ insert into st values ('a');++
++ return 0;++
++END bb;++*
But when I tried to execute this function, I got error "SQLCODE=-740, SQLSTATE=51034 is defined with the MODIFIES SQL DATA option, which is not valid in the context where the routine is invoked". Help me please. best regards, Turkin Andrew.