Calculating Readmit Rate

Hello,
If I have a patient's record as follows:

Lname Fname DOS End Date AdType Place Dicharge
John Smith 4/15/2009 4/27/2009 Initial Admit Hospital
Discharge to Home
John Smith 4/27/2009 5/1/2009 Initial Admit Home Still
at Home
John Smith 5/1/2009 5/3/2009 Re-Admit Hospital Dicharge
to NH
John Smith 5/3/2009 5/20/2009 Initial Admit NH Sill at
NH
John Smith 5/20/2009 5/25/2009 Re-Admit Hospital
Discharge to Home


I need to count how many times Re-Admit shows up in the AdType when
the person came from the NH (the last line). I don't want to count Re-
Admit if the person came to the Hospital from Home (in line 3). I
have about 50,000 lines of almost 20,000 patients. Can it be done?

thanks!