Hi Gareth Gareth,
This cannot be done with the GridViewSelectColumn, once a collapsed group is expanded, its sub rows will be selected if the "Select All" CheckBox is checked.
You can try defining your own custom column to control the SelectedItems.
TRY TELERIK'S NEWEST PRODUCT - EQATEC APPLICATION ANALYTICS for SILVERLIGHT.
Learn what features your users use (or don't use) in your application. Know your audience. Target it better. Develop wisely.
Sign up for Free application insights >>