Function GetCustomerList() As System.Data.IDataReader
        Dim connectionString As String = "Provider=Microsoft.Jet.OLEDB.4.0; Ole DB Services=-4; Data Source=" & server.mappath("db\super.mdb")
        Dim dbConnection As System.Data.IDbConnection = New System.Data.OleDb.OleDbConnection(connectionString)
        Dim strUN

        Dim queryString As String = "SELECT Customer.Username FROM Customer"
        Dim dbCommand As System.Data.IDbCommand = New System.Data.OleDb.OleDbCommand
         dbCommand.CommandText = queryString
         dbCommand.Connection = dbConnection

         dbConnection.Open
         Dim dataReader As System.Data.IDataReader = dbCommand.ExecuteReader(System.Data.CommandBehavior.CloseConnection)

         Return dataReader
End Function

Sub cmdSubmit_Click(sender As Object, e As EventArgs)
        GetCustomerList()
        If txtUserName.Text = !!!WHAT! WHAT do I have to do here!!! Then
              lblUsed.Text = "That username is in use. Please choose another."
        else
              lblUsed.Text = "OK"
        end if
End Sub

             While dataReader.Read()
                 if dataReader("Username") = txtUsername.Text then
                     label1.Text = "Username is already taken!"
                 end if
             End While