...
'The code below assumes that you have at least one summary in the root-level field layout.
Try
Dim val As Object = Me.xamDataPresenter1.Records.SummaryResults(0).Value
Dim summaryValue As Decimal = Convert.ToDecimal(val)
MessageBox.Show(String.Format("First summary value is {0}", summaryValue))
Catch
'fail silently
End Try
...