retrieving function raise messages in ecpg embedded sql code

I'm trying to get some additional information back from a trigger to my embedded SQL
program, to essentially emulate Informix's way of generating serial values.
I can get the serial to be generated, but I'm trying to figure out how to get the
generated value back to my program with minimal changes to the SQL.

I have a trigger that looks a bit like this:

create table mytable (mycol integer, mycol2 integer);

create or replace function functionfoo() returns trigger as $QUOTED$
BEGIN
new.mycol = nextval(TG_TABLE_NAME || '_mycol_seq');
raise INFO using MESSAGE = 'A Message';
return new;
END;
$QUOTED$ LANGUAGE 'plpgsql';

create trigger mytable_insert_trig before insert on mytable for each row when (new.mycol = 0) execute procedure functionfoo();

My ecpg program looks a bit like this:

exec sql begin declare section;
long mycol1;
long mycol2;
const char *mydb;
exec sql end declare section;
mycol1 = 0;
mycol2 = 1;
mydb = "mydb";
exec sql connect to :mydb;
exec sql prepare row_insert from "insert into mytable values (?, ?)";
EXEC SQL EXECUTE row_insert using :mycol1, mycol2;

I can't figure out how to retrieve the message raised by the trigger. I know it's
available in some cases, because I see the message when I insert a row through psql,
but even things like this:
printf("%s\n", PQerrorMessage(ECPGget_PGconn(mydb)));

return nothing useful. Is there a way to get this information?

Thanks,
eric