SERIAL + VB + ADO/SQL OLEDB?

Using a serial as the key in a table, I would like to know how I can retrieve the Value Informix has given to the serial. I'm using ADO 2.5 in visual basic 5.0 Over SQL OLEDB ODBC with Informix ODBC 3.31 DRIVER under it. I'm working with direct exec from the connection object like: cn.execute "insert into t (a, b) values (0, 5)",... (where for exemple a is my serial) I also tried SQL OLEDB INFORMIX 2.1 but then I have problems with my date fields i give in "DD/MM/YYYY" format. Using the SQL OLEDB ODBC, if I position DB_DATE under SETNET32 it work, but under SQL OLEDB INFORMIX it doesn't! I found no information on how to set environment variables, their names and possible values with the SQL OLEDB INFORMIX. Are there any interesting links on the net specific to SQL OLEDB INFORMIX for developper. thanks in advance.