How to modify navigation (page) onclick function

Hi Guys, I need your help. I need to modify some functionality of one of the site’s navigation menus. I added a new page “Function” and would like to change the actions everytime I click the button. Instead of redirecting to a page, I would like it to just remain on that page and will just popup a content. I already have created the popup content and would just like to insert it to the page. The question is, is this possible? and how? please…

Thank you