On Wed, 26 Aug 2009 20:39:01 -0700, brianpo
wrote:

Multiplying 111111111 by 111111111 in Excel 2007 results in
12345678987654300, which is obviously wrong.
Is there a way to improve the accuracy of results over 15 digits?
Thanks, Brian

You could download and install the XNUMBERS addin for EXCEL which performs
multiprecision floating point arithmetic up to 250 significant digits. By
default, it uses the precision of 30 digits.

You can Google for a source. I believe the latest version is 5.6
--ron