Are we to assume you have a list of documents, one per row, and that you
would like to retun a list of every document in every 50th row?
Assuming that is the case, then in any other column, though preferably one
next to the column of document references, pop a title into say B1 and then
starting in B2, put the following formula and copy down
This will flag the data on the 51st row, the 101st row etc (Assuming you
have titles in row 1 and so the 50th doc is on row 51).
If you actually want the docs on row 50 / 100 / 150 etc then just change the
1 to a 0