So what would happen in this scenario:

ordernum datetime agent
123456 01/03/06 7:00 33333
123456 01/03/06 7:30 33333
123456 01/03/06 9:15 33333
123456 01/03/06 11:00 33333

How do you know which ones to keep? You could delete the 7:30 and 9:15 records to have a 2 hour difference, but you could also delete the 7:30 and 11:00 records to accomplish the same. Or you could delete the 7:00 and 9:15 records too.