full width menu!

hello. i am trying to accomplish something but i do not know if it is possible. there is a slideshow plugin called slider revolution that i'm going to integrate below the header that is liquid, which i believe means it can take up the full width of the browser screen no matter how it is sized, and it will stay in proportion. so, i want to extend the menu bar out to be the same, 100% of the width of the screen. i realize this may not be possible because the menu bar is located inside the header/it is part of the header. any advice? perhaps with php? thanks