How to add column itunespurchasedate so I can identify the songs I bought in Itunes?

I know I can add many columns as well as modifying pre-existing ones, however I have a mix in my music collection, where half were bought on Itunes and the other half was ripped from CD's a long time ago. I want to be able to identify the songs that I have purchased from itunes, and have taken a look at the tags and say that itunespurchasedate is indeed a tag. I want to display that tag in the columns but whenever I try to find it, even when going to extended tags, it doesn't seem to find the field. This is mainly to help sort out what is bought from the itunes and what is not. Any ideas of how to accomplish this? I do not want to edit, I want to sort by and view.

See the documentation on how to customize the file list:

Also, you can filter for files that have a certain field with
%fieldname% PRESENT

where you replace %fieldname% with the right fieldname that you get from the extended tags dialogue.
You could try
%itunespurchasedate% PRESENT