Whatever the initial in-process solution is, you might also want to add another mechanism to make sure possible errors in the initial processing won't become catastrophic: add a scheduled agent (5 min) to process all new or modified documents and clear the credit card field in case it's not already cleared (as it should be). Make the agent send you an email as well to alarm you of potential trouble in the initial field handling.
Whatever the initial in-process solution is, you might also want to add another mechanism to make sure possible errors in the initial processing won't become catastrophic: add a scheduled agent (5 min) to process all new or modified documents and clear the credit card field in case it's not already cleared (as it should be). Make the agent send you an email as well to alarm you of potential trouble in the initial field handling.