In Numbers can you auto-populate a cell with a date when another cell is populated? I'm an avid Excel user and recently I've had to figure out how to use Numbers. So far I've been able to replicate all the Excel functionality that I use in Numbers... except for one thing. 

In Excel I can add the following formula...

=IF(A1="", "", IF(B1="", NOW(), B1))


This formula says when a value in added to cell A1 populate cell B1 with the current date. To get this to work you must turn on an Excel feature named iterative calculation (Options==>Formulas==>Enable iterative calculation).

I use this when I'm building an Excel task journal and I want to auto-populate the date. 

The important thing about this formula is that the date value is not updated another change is made. 

How can I do this in Numbers? How can I auto populate a date value in column "B" when a value is set in column "A"? It's important to keep in mind that once the date is set I don't want it to change.  

Here is my attempt at translating this formula in Numbers...

=IF(A2="", "", IF(B2="", NOW(), B2))


I get an error message in Numbers...

This formula can't reference its own cell, or depend on another formula that references this cell.


Thanks
Unfortunately, even if you were able to reference your own cell in Numbers, there is no assignment operator. 

Meaning that there would be no way to override the current value of the cell.