need to check for new updates and email a report only when there are new entries

I need a report to look for updates that occurred within  the past 30 minutes and then to email a report with those updates. I only want to email reports if updates have occurred in the past 30 minutes. I am running Crystal Reports 2013 and Business Objects 4;.1

I would schedule the report to run every 30 minutes but we need a mechanism that would email the report only if it contains data.

We have an web portal that users make entries in at random times and we need to be alerted of any new entries.

Any suggestions would be greatly appreciated.

Thanks

Bruce