Combobox update fail.

I have binding some textbox and a combobox to a Access database.

I can update the data in textbox, but the combobox will return to the oiginal value when I try to update the data.

Private Sub cmdSave_Click(...)

Me.BookTableAdapter.UpdateQuery(Me.BookDataSet.book(Me.BookBindingSource.Position).INDEX, txtISBN.Text, txtTitle.Text, txtAuthor.Text, txtPublisher.Text, cmbCodeSubject.Text)
Me.BookBindingSource.EndEdit()
Me.BookTableAdapter.Update(Me.BookDataSet.book)

End Sub

"UpdateQuery" is a Query I created in the Adapter

UPDATE book
SET ISBN = , Title = , Author = , Publisher = , CodeSubject =
WHERE ([INDEX] = )

The Combobox is bind to the CodeSubject column.

Can any one help me to solve this problem

Thanks.