Exclude Inputs

I want to have multiple events on objects for example

Press A get event 1 on object 1 Press B get event 2 on object 2

Press A + B get event 3 on object 1&2 , this is obviously pretty straight forward but what i dont want is to get either event 1 or 2 if both buttons are down. For example If each event is a sound i only want 1 to play not 3!

The simplest way would i guess be to exclude Multiple buttons from event 1 or 2 but is this possible simply ? , multiple commands are easy with && , is there "not" input command ??

Thanks