speakers and headphones "battle"!

[mahesh]

Hi to everybody. I m not newbie newbie but I ve a little problem.. I ve an speakers connected to the rear of my computer and also I ve my headphones. I want that when connect headphones, the rear speakers stop reproducing audio (like happens in Windows) and only works my headphones (front jack). Now.. if connect the headphones, both reproduce audio, glups! A pitty.. some comfortable solution? thanks!