Prevent pre-despatched orders from affecting the picking/packing reports

We've noticed as we've switched to PDAs we now are finding the picking/packing reports very helpful. However, there are just a few issues we still notice. If we pre-despatch any orders the day before when we know stock is due in the following morning these count towards picked/packed figures (which skews the figures). Can you have these excluded and just include 'Despatched' only?