MATLAB: Matrix manipulation by function

Question

Dear all, For a given matrix (square) i need to eliminate some elements (some rows and columns)

A = 
    35     6    19
     3     7    23
    31     2    27

I need only the second (not the first and the third) row and column : the eliminated are stocked in a vector

B = (1 3)

So : some function (A, B) :::> the result C = 7

function (A, B) = C

Answer 1

ii = num2cell([1;1]*setdiff(1:length(A),B(:)'),2);
out = A(ii{:});