How can I capture a URL Parameter on a list page so that I may append it to the URL of an "Add New Item" button?

Question

Scenario: I have a list page that has already been filtered from a prior table via a URL parameter. How do I carry that URL parameter over when "create a new item" button is clicked?

Issue: On the form page itself, I have no problem getting the URL parameter from the URL to populate the form field itself. I just can't figure out how to get that parameter added to the URL from the previous filtered list page when the "add new item" button is clicked.( at least find a solution that works ).

Any help would be graciously appreciated.