Calling a function via ODBC

Hi,
I have postgres installed on my Machine (MacOSX) and connect to it via
ODBC from my C app.
All works ok (select, insert, update and so on).

Now I made the following simple function:
CREATE OR REPLACE FUNCTION concat_text (TEXT, TEXT) RETURNS TEXT AS '
BEGIN
RETURN $1 || $2;
END;
' LANGUAGE 'plpgsql';

and called it succesfully doing:
SQLExecDirect(... ""select concat_text('val', 'erio')"" ...)
and fetching the result with SQLFetchScroll etc..., all works ok.

SO WHICH IS THE QUESTION?
THE QUESTION IS:
Is there a way to call my func using the ODBC syntax:
{? = CALL concat_text(?, ?)}
using SQLBindParameter to bind variable (input/output) to '?' and
getting return value directly in a bound var (without any Fetch) (see
http://www.ddart.net/mssql/sql70/odbcht10_1.htm )?

Does someone have an example in using SQLBindParameter to set parameter
IN and get return value OUT?

Thanks for help
==================================================================
Valerio Ferrucci Tabasoft Sas
ferrucci(at)tabasoft(dot)it http://www.tabasoft.it