Martin Gross <m-gross@gmx.net> writes:

> Dear Michael,
>
> thank you very much, this is what I was looking for.  I myself
> supposed the answer should be related to "remote references", but was
> not sure how to use them.
>
> Just one point is not yet optimum to me: I do not have just 2 tables,
> but hundreds.  It would be hard and not very clean to add them all one
> by one.  Do you know if it there is a better way to reference remote
> tables?

Not a pure Org-mode solution, but something like the attached could be
used to sum up a particular column from every table in a file.  Not
flexible but possibly sufficient.