What movie is this? It starts tom hanks or bill murray...?

I believe this film stars Tom Hanks or Bill Murray although when I checked there Wikipedia pages I found no such record of the film. Within the film there are two brothers, the one brother who I believe to be Bill Murray or Tom Hanks comes to visit the other brother for this birthday, although the other brother has some sort of dinner with clients already trying to sell them something/show profits or something along that and to keep the other brother busy he gets him to do some sort of real life acting (not sure what its called but its him acting through a script running around the city with the real actors) although when he is about to start he gets a call at a phone booth that is supposed to be were the acting people will call when there ready but people wanting someone assassinated call and he thinks there the acting people so he goes along with it meets up with a girl kills some other people and it goes along like this mostly being comedic and such along the way. Anyway sorry if I put to much description in I just wanted to make sure you could be sure about the films name.

But for short and simple, it might star tom hanks or bill murray and revolves around a man thinking hes in the real life theatre although hes actually mistaken for a spy so he kills people and such.