Data Merge SetUp help

Ok, I have a spreadsheet that a client gave me that will be used for a Data Merge. It lists Patient Names/Addresses as well as their respective Doctors. Most all of the Doctors listed have multiple Patients.

ie:
Patient Name | Patient Address | Doctor Name | Doctor Address

Mary | NY | Dr. Ross | NY
John | NY | Dr. Ross | NY
Tim | NY | Dr. Ross | NY
Jane | MI | Dr. Moore | MI
Jacob | MI | Dr. Moore | MI


The Patient name/address is in the same row as their Doctor's name/address, so I basically have multiple records of the Doctor for each patient. The merged letter that I need the data for will have the Doctor's name/address at the top of the letter and ALL of their Patient's names/address at the end of the letter.

My question is this: How do I automate Excel to see the Doctor's names and then list all of the Patient names attached to said Doctor without reading the wrong Patient names? (the patient names are listed first by the way)

The letter will be formatted like this:
-------------------------------------------
<Doctor Name>
<Address>

Here is the text of the letter...

<Patient 1>
<Patient 2>
<Patient 3>
-------------------------------------------

I have attached a sample with only a few names. The actual list is about 1000 different names.

Any help with this matter would be greatly appreciated.