Autoincrement Autokey in ONNM

Hi,

I've an user table linked to an Object. I've linked my user fields to TextBox and combo on my Form, when I save, SAP autoincrement the AutoKey value on ONNM table, but if I do an INSERT query Autokey value doesn't autoincrement. How I can increment automatically it's value? only with an UPDATE? is there another way?

Thanks