How setup and access underlying ID's in selected Rows in a wpf DataTemplated ListBox?

I've populated a wpf ListBox using a DataTemplate in xaml and a System.Data.DataSet in the vb.net code behind. I've sneeked in a underlying numeric database ID in a DockPanel ToolTip of the DataTemplate. My question: Is there a simple way to reference these ID's in the Click event of the ListBox? I wish to store and act upon multiple selected ID's without hard coding specific Classes or ObservableCollections. In VB6 I would have simply stored the ID's in the ItemData property of a ListBox.

Gouranga Gupta :-)