I am sad to tell you that the calculation of PD is very dependent on your situation and data and assumptions that you make. There is no one general formula that can be applied to a data set to compute PD. Where I work, the PD calculations are different for mortgage loans and auto loans, and so on; other banks probably do it differently than we do.
Your question about how to calculate PD is best answered within your company or university. We can help with the SAS once the method of calculating PD is determined, but I doubt someone here can determine how your organization should calculate PD.
On a side note, most people here refuse to (or are not allowed to) download Excel files. So I have not looked at the data in your Excel file. Best to provide a portion of your data as text, as working SAS data step code (examples and instructions) included in your message by pasting it into the window that appears when you click on the little running man icon, but I don't see a need for you to do that right now as determining the method of calculating PD is the first thing you need to do.
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Paige Miller