This is the very elementary array index operation. To retrieve the specified data, just use
If you'd like the retrieved columns to form a new matrix by their relative positions in S, simply code
A = S(:, 200:25:700)
A is an m-by-201 matrix, m being the number of rows of S. If you'd like to assign the extracted data to a portion of a new matrix, make sure that the destination portion can also be arranged as an m-by-201 matrix, e.g.,
A(3:m+2, 5:2:405) = S(:, 200:25:700)
A being the already allocated new matrix (hope I haven't made mistakes).