Change CnP Pledge "Pledge End Date" to enter a previous date

[esowers]

We are importing historical pledge records into salesforce and have found that the "remaining/excess balance" field does not auto-calculate after insert. When we try to activate the trigger by clicking edit and save on the Pledge record, we receive an error that our Pledge End Date is not "today or in the future." I assume this is done to protect from changing that date to be prior to the last gift date, however in our case this is a problem.

Thanks!