BUTTONS MAKIN ME CRAZY !!! :(

i want one button which can show/hide a layer...
i can put 2 different buttons... one 4 showing -n- one 4 hiding da layer... but how 2 get only one button do both things !!!
plz help
i can put 2 different buttons... one 4 showing -n- one 4 hiding da layer... but how 2 get only one button do both things !!!
plz help
