I need to add a button or change in the code where the home button send you

I need to be able to add a button that sends the viewer back to the entire site's home page .... I am running my wp in multisite mode and now it sends the viewer to the home page for that particular site but I need it to goto the homepage for all the entire site... is there a way to change to coding for the button the exist now ? or can I code in another button ? if so how ?