pl/pgSQL sequence question

Hi,

I'm attempting to build a table within a pl/pgsql function that is to be populated so that it has an index column
1...N. (without looping).  I used to do this in sybase and found it extremely useful) 
So to try and acheive this I:
A, Create a sequence for the identiy column, then place this as the default value in the table.
B, Use a large table and a limit on the select to populate with the correct number of rows.
The problem is that the table does not seem to see the sequence and the function fails:-

CREATE or REPLACE FUNCTION debugMe(integer,resolution) returns integer AS '
   DECLARE
      size alias for $1;
      resolution alias for $2;

      createseq varchar(200);
      createtable varchar(200);
      dropseq varchar(200);
      droptable varchar(200);

   BEGIN
      --sequence commands
      createseq := ''CREATE SEQUENCE 'tmp_seq INCREMENT ''||resolution|| '' MINVALUE 1 START 1'';      dropseq   :=
''DROPSEQUENCE ''||seqname; 

      --table commands
      createtable := ''CREATE TABLE debugtab(idcol INTEGER PRIMARY KEY DEFAULT NEXTVAL(tmp_seq), value int )'';
      droptable := ''DROP TABLE ''||tablename;
      --insert data commands
      loadtable := ''insert into debugtab(value) select 0 from largetable where positivenumber > 0 limit ''||size;

      --A
      execute createseq;
      --B
      execute createtable;
      --why can it not find tmp_seq??

      --C insert data, not a worry at the moment
     execute loadtable;

      --D do the major processing

      --Z clean up
      execute dropseq;
      execute droptable;

   END
' LANGUAGE 'plpgsql';

error message:-
NOTICE:  line ?? at execute statementERROR:  Attribute 'tmp_seq' not found
Hope someone can help
Many thanks,
Steve