Private Sub TextBox1_TextChanged(ByVal sender As System.Object, ByVal e As _
  System.EventArgs) Handles TextBox1.TextChanged
        oConn.Open()
        Dim oCommand As New OleDbCommand("SELECT Artikel FROM Tab_Barcode WHERE" & _
          "Barcode=" & TextBox1.Text, oConn)
        TextBox2.Text = oCommand.ExecuteScalar()
        oConn.Close() 
End Sub

Those people who think they know everything are a great annoyance to those of us who do - Isaac Asimov