add new datagridview row to database

Writing in vb.net, I allow the user to add a new row to a datagridview.  On row leave, I validated to see if the appropriate cells have values, planning to insert the data into a database.    The last cell in the row is not populated when validated.   If I go back to the row, the cell is recognized.   The problem I have is that I update rows that exist and insert new rows.   If the user leaves a row without validation and then goes back, the new row in the database is not there to update.