checking for existence of a table in plpgsql.

hi,

here i use postgresql 7.2.

how can one know that a particular table exists or not in plpgsql?

need is something like this.. 
from plpgsql, i wish to insert a record in a table (create and insert,
if not exists).

---

create function ftest()
returns int as 'declare

begin
 if <table exists> then   insert into <table> (...) values (...); else   create <table> (...);   insert into <table>
(...)values (...); end if;  return row_count;
 
end;'
language 'plpgsql';

----

hope to get some lights.

Regards,
Bhuvaneswaran.