Use 'Custom' and then use the formula
=B1=""
(you should be able to enter simply B1="" and Excel should insert the
leading = for you).

"apache007" wrote:

Hi guys,

I have user input on cell A1
and check cell on B1

After User enter his data on A1 and if the data is correct, manager fill
CELL B1 to confirm the entry.

After the manager fill CELL B1, we do not want any user to change A1, before
deleting B1 first.

What formula should I use in DATA VALIDATION to prevent deleting data on
Cell A1, when B1 is not empty?

Thanks in advance.