Question: Command line code for Creating a new Document Property or Attribute

Ok so as title says that is what i need, or the process of changing the document property listing that is generated when i start a new worksheet. 

The reason being is that of course the obvious solution is for me to have a personalized template for a worksheet with the desired attribute listing, which i have, but the trouble is i have already generated a large number of archive entries in a database or "library" of worksheets that i am building that have the standard attribute listing, and for the new functionality that i have chosen i rely on having the specific custom attribute listing for the new template, and i want to implement this functionality into use for the existing database entries as well as the future ones created, without having to copy and paste things for each of the existing entries for the obvious reason that this is boring and annoying