Logic circuit for buttons... i need definitely some help.

Hi,

after the success on my last patch the new patch gave me a really bad headache in the last couple of hours. :) i try to build something like a logic circuit to control the behavior of 4 buttons. basically i want that you can switch ON/OFF the buttons 1-3 (individual). if the buttons 1-3 are ON button 4 is OFF, if the buttons 1-3 are OFF button 4 should be on. also if only one or two buttons from the buttons 1-3 are ON, button 4 should be in the OFF position. that means button 4 is only on if the buttons 1-3 are all in off position.

hopefully you can follow me. i´m not a native speaker and sometimes it can be pretty hard to describe the idea of a patch in an easy way. :)

could please someone push me in the right direction !? underneath you can find my current patch but i cant go any further with it. i have got no idea how to use the if, then, else command in a way that it works for me. maybe there is also a another workaround. would be interesting what you think about the thing.

thx

seb