You do not need to do this. When you insert the record, the database will automatically generate the autonumber required and report it back to you. It is much easier to report this information AFTER the insert has been done.
If you want to report it before the insert, then you actually have to insert a blank record to 'reserve' the autonumber. Without the proper care, this leaves blank records, incomplete data, or non-sequential records in your database. In other words, you can get the autonumber before inserting, but you have to make sure you are managing it correctly.