Here is code you can use in teh TableControlCellClick event to get the clicked value.
'' subscribe to the event
AddHandler Me.gridGroupingControl1.TableControlCellClick, AddressOf TableControl_CellClick
''the event handler
Private Sub TableControl_CellClick(ByVal sender As Object, ByVal e As GridTableControlCellClickEventArgs)
Dim cc As GridCurrentCell = e.TableControl.CurrentCell
Dim style As GridTableCellStyleInfo = e.TableControl.Model(cc.RowIndex, cc.ColIndex)
Dim recRow As GridRecordRow = style.TableCellIdentity.DisplayElement
If Not recRow Is Nothing AndAlso Not recRow.ParentRecord Is Nothing Then
Dim val As Object = recRow.ParentRecord.GetValue(style.TableCellIdentity.Column.MappingName)
Console.WriteLine(val.ToString())
End If
End Sub