Macro to copy and paste to new page

Hi,

I'm trying to create a macro in Microsoft Word which allows for an "add to cart" type of functionality.  I have a 150 pg document with item #'s throughout, and I want users to be able to double-click on the items #'s and have the double-click trigger the item # being copied and pasted to a new word document, with each subsequent double-click pasting to the newly created word doc as a delimited list with a comma separating each number.  Also hoping for a validation that prevents duplicates.  

So, for example a user opens the word document, double-clicks on "1234", a new word document, call it "List", opens with "1234" pasted at the top.  If the user then goes and double-clicks "5678", it will paste that into the "List" doc so that the list doc reads "1234, 5678".  If the user is then to double-click "5678" again, it would recognize that this is a duplicate and not paste to the "List" doc a second time. 

All of the item #'s in the document are hyperlinked/underlined if that helps for identification.  

I'm pretty clueless when it comes to Macros and could use some help, if anyone is able to assist. 

Thank you VERY much!