Check out the search portals in this demo file and let me know if they do what you wanted or not:
(The left hand portal could use this filter expression:
IsEmpty ( Invoice::gSearchField1) or PatternCount ( Products4Selection::ProdDesc ; Invoice::gSearchField1 )
To list all product records when there is no search text in the search field.
Yes they have certainly pointed us in the right direction...many thanks for that