Re: mark-sexp signals "Containing expression ends prematurely"

[rgb]

> However if point or mark bump into a curly brace, that is { or },
> mark-sexp signal the "Containing expression ends prematurely" error.
> What I want to do in this case is that the region should extend only on
> the other side until the whole { } bock is in the region.

You want to surround the expression signaling the error with the
(in my opinion, unintuitively named) condition-case statement.
That will give control back to your function when the error occurs.
You can then take a different action like backward-up-list or
down-list.