Which movie (1970s comedy) ?

I remember a movie, probably from US or UK, a funny comedy in the style of Pink Panther, possibly from 1970s. Someone is carefully planning some robbery (or some murder?), he sees himself climbing on a train, jumping on the roof, doing this and that, all perfect. But when he actually does it, all is not so easy, he can not really jump like that, and the plan doesn't work so well.
Which movie could it be? Which actor?

Was it a Woody Allen film? Take the Money and Run?

No, not a Woody Allen film. Too bad I can't remember an actor..

Try Unfaithfully yours (1984)

"Try Unfaithfully yours (1984)"
A composer suspects his wife of cheating. He plots to kill her and frame it on her lover.
Stars: Dudley Moore, Nastassja Kinski, Armand Assante, ..
-- Yes, I think it is. Won't know for sure until I watch, but I think that's it.
Thanks! Could never have found it by myself.

I don't know what movie you're looking for, but based on your first post, I doubt that it's Unfaithfully Yours. In that movie, Dudley Moore plans a murder, but there's nothing with climbing on a train or jumping on a roof. It's a pretty basic plan without much action, and it takes place in his office, a restaurant, and his home.

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Yea, it's not "Try Unfaithfully yours (1984)".

I remember someone planning a robbery(?) involving a train.
They plan carefully, with a meeting in which some animation preview shows how it will easily be done. One guy like an athlete jumps on a train, jumps between wagons, jumps on the roof, etc.. But when they do it, they can not. It's a comedy, not a serious crime movie.