I have fought with this for 2 days and I am trying to have a worksheet cell update the date and time if the cell it is referencing (B3 see below)

Here is the formula I am using however it updates every time a new row is added to the worksheet. So the Date/Time stamp on each row is always updated to NOW() everytime.

=IF(ISNA(B3),"0/0/00 00:00",NOW())

I would like to have a Date/Time stamp stay as is once that row has been added. Is there anyway to stop the field from updating once the date and time have been set?

ARGGHHH!!