Here is an example...I have a BO called InvoiceMasterBO.  The BO has a custom property called 'grandtotal' which summarizes the finance info on each invoice.  I need to send a batch of these invoices to the accounting system.  For a double check and a requirement of the accounting system, I need to export the SUM(grandtotal), too.  How do I do that?

This is probably so obvious that I will kick myself as soon as I find out how to do it.

Thanks,
Bill