Problem receiving function return thru RDO connection with ORACLE

Within a VB5 program, we once had a call to an Oracle function (which was returning a Number value) and everything was going fine. We used a RDO connection to Oracle, without a declared DSN. We used the Microsoft ODBC driver for Oracle.
For a reason of our own, we decided to change the driver. We replaced it by Oracle's Oracle73 ODBC driver. Then we had some trouble to established to connection. We fixed it and now we're face to another problem we failed to fix! The call to the function still works but it seems unable to return the value to VB. We get the Oracle error 06502. I tried the same call without ODBC (using SQL*Plus) and it worked fine. I traced both (VB and SQL*Plus) and I found out that both seems to work the same and goes well thru the function. It's just that in the case of VB, the return value cannot be returned.
The call to the function is made as the following: Set qryQueryRDO = conConnection.CreateQuery("", "{? = call iF000_maj_in_plant('parms')}")
Can anybody help us to make it work? Thanks.

-- 
Michel Gauthier
qgmi1_at_qbc.clic.net
Produits Forestiers Donohue Inc.
The ideas expressed/language used reflect those of the author,
Not necessarly those of Donohue Inc.