Excel's documented limit is 15 digits; you cannot change that. You
could enter longer numbers as text, but could not calculate with that
extra precision. Through VBA you could use up to 28 digits (no
scientific notation or math functions other than +-*/) with the Decimal
data type. I've never used it, but the XNUMBERS add-in claims to handle
numbers up to 200 digits, and includes transcendental math functions:
http://digilander.libero.it/foxes/index.htm
You can download a 64 digit calculator from
http://www.crbond.com/applications.htm
but the version I tried did not support copy/paste.
I don't know what a fractional digit would be in your context, so I
assume that you want to deal with 100000 (10^5) digits, although I can't
conceive of an application that would need that (far too few digits for
calculating any natural constant to record precision, and far to much
for just about anything else).
For that kind of precision, you might do better to look at symbolic
engines with arbitrary precision, such as Maple or Mathematica. If you
are not prepared to spend $$, you might try Maxima
http://maxima.sourceforge.net/
but the interface is a bit dated.
Jerry
