Is there a standard backlog report for Work Orders in EAM?

We are writing our own backlog report but wondered if there was a standard report Oracle supply? We are struggling to pin a date down in the system because users can move the dates and bring the Work Order out of backlog. We were thinking the Scheduled Completion Date is the one to use as this is the last date/time the work must be done before the work goes into backlog. The only issue we have found is that the users can move the Schedule Completion Date themselves so we're now thinking we need to make that field read only