adding previous day's efforts in total discharge time

There is an article in TODAY'S HOSPITALIST, June 2011 that states "you can add the previous day's efforts in discharge preparatio to your total discharge time".
So...my Hospitalist documents a subsequent visit and bills 99232. He then dictates the discharge summary and indicates 25 min discharge preparation. The next day the patient is discharged and my Hospitalist that day adds an addendum to the discharge summary indicating an additional 10 min discharge preparation. I can add the two times together (from different days) and bill 99239 on the discharge day?????