Using ADO

You cannot have calculated or lookup fields of the type TWideStringField. It is a bug of Borland's implementation of TADODataSet. The best workaround is to modify the DB.PAS that add ftWideString to CalcFieldTypes declared in TDataSet.BindFields.
To use effectively ADO, I suggest downloading the MS SDK platform. Without it, it is often difficult to understand the inner workings of TADODatasets.
Take some time to learn the ADO SHAPE SQL extension command after downloading the SDK platform. It might be useful to you. The default installation of Delphi includes an example that demonstrates the use of SHAPE command.