Do you need to recalculate? Is recalculation set to automatic?
In 2007, check for:
Office buttonExcel OptionsFormulasWorkbook CalculationAutomatic

Regards,
Fred

"SMW" wrote in message
...
I tried ISNA(A1) - both by selecting all cells and applying the conditional
format, and then by selecting individual cells and giving each one the
same
formula under conditional formatting. The formatting did not change back
from white when #N/A changed to a valid data value.

(I'm using "Formula is" rather than "Cell Value is.")

"Gord Dibben" wrote:

I would not use ISERROR which masks all errors but then I'm not an
Internet
guide.

I would use ISNA which is specific to your needs.

Your formula has absolute reference to $A$1

Each cell in the range looks only at $A$1 for the condtion.

Remove the $ signs.

=ISNA(A1)


Gord Dibben MS Excel MVP

On Wed, 6 Jan 2010 16:04:01 -0800, SMW
wrote:

I'm applying the conditional format =ISERROR($A$1) to change the text of
cells displaying #N/A to white, as recommended by every conditional
formatting guide on the Internet. However, when applied to a range of
cells,
they all turn white!!

Cell A1 has a formula that provides a #N/A error, in the same way that
the
desired cells produce an #N/A error:

The cells that need to be white are coded =VLOOKUP(B4,SHEET1,10) where
B4 is
='SHEET2'!C4. C4 is blank, so B4 returns 0. The result is #N/A. (When
C4 is
no longer blank, B4 displays data and needs to be visible.)

This is the only conditional format used in the spreadsheet. I've tried
to
find out if anyone else has this problem and had no luck.

.