external UDF problem

Hi everybody,

i'm trying to get my hands wet and dirty with UDFs. i need to access a
subprocedure of a service program. the service program is created. the
udf is created/registered. but when i try to use the udf in an sql
statement it says that it can't find the function

SQL0204 SUBSTRINGMERGE der Art *N in *LIBL nicht gefunden.
(SUBSTRINGMERGE of type *N in *LIBL not found.)

i can access the subprocedure from another rpg program. no problem
there.

subprocedure prototype:
D import_substringMerge...
D PR 1000A
D dest 1000A
D source 1000A


sql for creating the function:
create function substringMerge (dest char(1000), src char(1000))
returns char(1000)
language RPGLE
specific import_substringMerge
deterministic
no sql
returns null on null input
no external action
not fenced
external name 'OBJEKTTEST/IMPUTIL_SV(import_substringMerge)'
parameter style general;


my sql for testing:
select substringMerge('test', ' x ') from sysibm/sysdummy1

and is there any way to specifiy *libl in the external name for the
service program?

thanx in advance

Mihael Schmidt