The most sophisticated import/export interface is to BibTeX since WibTeX's own database is organized very similar to standard BibTeX. You may as well import data via CSV (comma separated values) which in turn can be passed through Microsoft Excel. Make sure that the layout of the data to be imported match WibTeX's database fields. To be on the safe side, you can first export an empty CSV file from WibTeX to see the layout in Microsoft Excel. Then, fill the empty columns with your data and re-import to WibTeX.