After you set one of the buttons for function, did the 2nd function column go to normal from grayed out? If so, the next thing to do is to set at least one button for a 2nd function, and make sure to check the mode reset timer (I have mine at 3 seconds). Once this is done and you write it to the radio, when you press the button you have set for function, does "FNC" show up in the upper left corner of the display screen? If so, you should be able to then press the button you have set for a 2nd function and it should work (make sure the mode reset timer has not expired, when it does, the "FNC" will disappear from the screen)..
I have my 3180 radio set up for function to be the side 2 key, and the "A" button has scan delete/add for the 1st function and low power for the 2nd function.
Let me know if that works for you.