I have a report with a {date time} field in each record. My report is grouped by a {batch number}. Each batch has 2 records in it. The records are defined by an {activity type} field. The activity field value is either "start" or "end". I would like to be able to determine the time difference in minutes between the {date time} field of the {activity type}= "start" record and the {date time} field of {activity type}="end" record in my {batch number} group.

I have read and looked and attempted to complete this without success.

Any help would be greatly appreciated.