When Excel is asked to do an arithmetic operation ( add, multiply, etc)
Boolean values (True or False), it treats TRUE as 1 and False as 0. The
double negation (please note that ++ is also double unary) is one such
arithmetic operation.
It does the same thing if the cell has text that can be represented as a
number.
But it is not clear what the purpose is in the example. Can you tell us what
is in the cells?
best wishes
--
Bernard V Liengme
Microsoft Excel MVP
http://people.stfx.ca/bliengme
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"Daren" wrote in message
...
Hello,

The AND statement is as follows:

=and(--d2--c2,--c2--b2m--b2--a2).

What's the purpose of the double unary here?

Thanks!