If the numbers are what mathematician call "real numbers" - have deceimal
point as in 1.23 - then a simple sum like =a1+b1-c1 may give a value that
not quite zero even thought zero is expected. Not just an Excel problem but
a computer problem (round -off error) resulting from how the IEEE convention
( see one of the links below) converts decimal numbers (base 10) to binary
numbers (base 2).
Try =ROUND(A1+B1-C1,12) to round the result to 12 places of decimal and
avoid the n'round off' error problem


Chip's clear explanation
http://www.cpearson.com/excel/rounding.htm

Floating-point arithmetic may give inaccurate results in Excel
http://support.microsoft.com/kb/78113/en-us

(Complete) Tutorial to Understand IEEE Floating-Point Errors
http://support.microsoft.com/kb/42980

What Every Computer Scientist Should Know About Floating Point
http://docs.sun.com/source/806-3568/ncg_goldberg.html

Visual Basic and Arithmetic Precision
http://support.microsoft.com/default...NoWebContent=1

Others:
http://support.microsoft.com/kb/214118

http://docs.sun.com/source/806-3568/ncg_goldberg.html

best wishes
--
Bernard Liengme
Microsoft Excel MVP
http://people.stfx.ca/bliengme



"jungbugg40" wrote in message
...
I have a spreadsheet with 4 columns; the 4th columns is a formula going
across the 3 columns a+b-c = d with d preferably equally zero. When I
format
column d almost all of the columns that equal zero display as a dash
(preference). However periodically one or two of the rows will display as
0.00 and I can't seem to get the formatting to change to the dash. I have
tried to reformat all columns all other cells and to no avail. Has anyone
else run into this issue and if so how have u solved it. The only way I
can
solve it is to actually put a zero in the cell.