How to return messages from an Oracle DB to an MS Access client?

[Sean Ryan]

I have an application that works as follows. Users,
in MS Access, query against link tables. The Link tables
use an ODBC data source to connect to an Oracle database.
If a user action results in an Oracle error that error
message is returned to the client, MS Access. This all
works fine.
I want to raise application specific error messages
in the Oracle database and have those messages returned
from the Oracle database to the client. If I use an
Oracle client, line SQLPLUS to connect to the database I
do get the messages but when I connect from MS Access, as
described above, I do not see the messages. What a I
doing wrong?

Thanks,
Sean