FETCH a cursor inside a SELECT

I've been working with this all day, and I'm finally out of ideas.
Hopefully someone has encountered a situation like this before.

Originally I was going to write a function that returned a series of
id's, but this caused no end of confusion on PG 7.2.3. Instead, I've
decided to return cursors.

matchClass1 works as expected. However in matchClass2, I wish to exclude
all of the results from matchClass1. This inline fetch gives me the
following error calling matchClass2:

---
=> BEGIN; SELECT matchClass2('ref1', 0); COMMIT;
BEGIN
NOTICE: Error occurred while executing PL/pgSQL function matchclass2
NOTICE: line 6 at open
ERROR: parser: parse error at or near "ALL"
COMMIT
---

The functions are:

CREATE FUNCTION matchClass1(refcursor, integer) RETURNS refcursor AS '
BEGIN
OPEN $1 FOR SELECT MyId FROM MyTable;
RETURN $1;
END;
' LANGUAGE 'plpgsql';

CREATE FUNCTION matchClass2(refcursor, integer) RETURNS refcursor AS '
DECLARE
class1 refcursor;
BEGIN
class1 := matchClass1(class1, $2);

OPEN $1 FOR SELECT MyId FROM MyTable WHERE
MyId NOT IN (FETCH ALL IN class1);

RETURN $1;
END;
' LANGUAGE 'plpgsql';

For the sake of simplicity, I've stripped away the where clauses (about
25 lines each, hence my want to do this).

Can anyone offer any suggestions?

Thanks,

David