Circular references are caused when the result of a calculation is includedin
the calculation itself. An example would be if A5 contained the formula
=sum(A1:A4), but A2 contained the formula =A5.
Circular references are usually accidental errors, but there are some uses
in engineering calculations I believe.
I expect you would be more interested in how to identify where they are
-- look at the statusbar for the cell number
-- advance through the worksheet tabs until you see the circular reference with a cell number.
But you asked how you could use -- keep in mind that very few users would
even want to use them -- was going to point you to Stephen Bullen's site
but looks like it is in his books. You would have to search Google Groups
for some of his postings. --- author:stephen.bullen circular.reference
