Just some thoughts ..

Assume we have input a "reference" date and time
in A1: 16-01-2005 3:16:22 PM (example)

And our working range is say, in A2:D5

Select A2:D5

Click Format Conditional Formatting

Make the settings for Condition 1 as:
Formula Is | =AND(NOW()$A$1+1,ISBLANK(A2))
Click Format button Patterns tab Light brown? OK

Click OK at the main dialog

The above will trigger the conditional format
for all empty* cells within A2:D5
after 24 hours from the reference date/time in A1

If there are formula cells within A2:D5
which could evaluate to ""
and you want these cells to be treated like "empty" cells
if the formula returns are "",
just change the conditional format formula above to:
=AND(NOW()$A$1+1,A2="")

--
Rgds
Max
xl 97
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GMT+8, 1° 22' N 103° 45' E
xdemechanik <atyahoo<dotcom
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"BT" wrote in message
...
How can empty cells automatically highlight after 24 hours?