Hi Barbara,
You can't individually describe each argument in turn, but you can
enter a general description
..
It is a good idea to maintain separate documentation for anything
you do.
The parameter cell will show up in the Function Wizard Help without
any intervention, so choose your parameter names carefully. The
description can be entered as follows: Alt+F11 (VBE), F2 (View,
Object Browser), Select the module (or <globals>) on left, select the
function on right, RClick, properties, fill in description.
Description information for a Function (#fundesc)
http://www.mvps.org/dmcritchie/excel/formula.htm#fundesc