Extraction and sum of values in an array

It would be easy to write a function for your yellow expressions, but concerning your green expressions you demand too much for at least two reasons:

1) A user defined function can't have a variable number of arguments. You have to decide whether RESULT() should have two or just one argument.

2) Life would be much easier if we could agree on that the second function argument always indicates the columns in the matrix and not one time the columns and the other time one additional row. Furhermore - how should RESULT() know in the screenshot above that you mean just the firrst column?

Of course it would be possible to implement RESULT() in such a way that in case the second argument is not a valid column number but a string that it meant as an additional row indicator and column(s) should default to 1 in the special case. But I would strongly advise against that kind of (very) special rule.

So something like the following is easy to implement, but your green examples -- harder (2nd argument is row, too) up to impossibe (function with either one or more arguments).

So it possible enter the arguments of the two ways.

Thank you very much Werner and also to Stuart for your suggestion.