Dear Duke,

I only put my question in a few hours ago, and already three people,
including yourself, have given me the solution. You can struggle for hours
with such things, so I am very grateful for your help.

Thanks a lot, and may I take the opportunity to wish you a very Happy New
Year at the same time.

"Duke Carey" wrote:

Encase your existing formulas within the MAX() function

=max(rate of return formula, -100%)
=max($ amount formula, 0)

"David Drennan" wrote:

I use Excel to record my investments. I project numbers on the basis of "If
the rate of change so far in this share continues for the rest of the year,
what will be the year-end outcome?" My cell formulae work well, but . . .
(a) How do you restrict the answer cell from being worse than -100% (I
can't lose more than my original investment), and
(b) How do you prevent the £ or $ amount being less than zero?

For the life of me, I cannot find the answer in Excel Help. I have tried
using 'Solver' and 'Data Validation', but having entered the values I want,
my instructions are then ignored.