Why only sorted When i click Second Time

[chinhow]

Private Sub cboAddSupplier_SelectedIndexChanged(ByVal sender As Object, ByVal e As System.EventArgs) Handles cboAddSupplier.SelectedIndexChanged
DataSet41.Clear()
OleDbDataAdapter4.SelectCommand.CommandText = _
"SELECT * FROM Item WHERE " & _
"Supplier = '" & cboAddSupplier.Text & "' " & _
"ORDER BY Item ASC"
OleDbDataAdapter4.Fill(DataSet41)

End Sub