Either of these

=IF(B1<"",A1+B1,A1-C1)

=IF(B1="",A1-C1,A1+B1)


Gord Dibben MS Excel MVP

On Sat, 27 Oct 2007 07:09:00 -0700, FC wrote:

Thanks for the formula, but it did not meet the requirements. I know is
almost that one but can not make it up!!!
Thanks for repling.
"Nick Hodge" wrote:

FC

You need an IF function, like

=IF(B1="",A1+B1,A1-C1)

--
HTH
Nick Hodge
Microsoft MVP - Excel
Southampton, England
DTHIS
web: www.nickhodge.co.uk
blog (non tech): www.nickhodge.co.uk/blog


"FC" wrote in message
...
I need a double formula if that's possible.
1 Worksheet A,B,C,D from 1 to 100 all columns.
For explanatories purposes I ll use just the first row ( formula will be
copied down to 100)
D1=A1+B1
but if there is not value in B1, then it will be a value in C1 and the
formula instead of adding will sustract. D1=A1-C1
A1 will always has a value
B1 and C1 will alternate ( one of the 2 is empty while the other has a
value)
D1 will be the total, either from adding B1 or sustracting C1( depending
who
has the value) from A1.
Legend : value= number
XL 2003