Subtotal list by TimeStamp component?

andy

Anyone know if it's possible to sub total a landmark list by a TimeStamp component using a date operator?

For example a given list has a "RunTime" TimeStamp field and an "InvoiceCount" numeric column. There can be multiple RunTimes a day and the desire is to total the InvoiceCount each day. If a subtotal is added to RunTime then there is a subtotal for each RunTime, but if the "date" operator is applied to the RunTime sub total no subtotal rows are displayed.

RunTime

            sort order is ByRunTime

                is default

                Subtotal By

                    RunTime date

InvoiceCount

            total