Functions IF and NOW

[Varko]

MS excel 2007

I have sheet with multiple rows and columns, for example I'd like to put formula in cell B2 like =IF(C2 <> "";NOW();"") and I want to fix this date without changing it with operating system, just to remember the moment of entering cell C2 and lock the column B.

I read something that this might isn't possible, and can work with VBA code but I am really looking for any other simple solution if it is possible

[#2]

@Varko 

Without VBA if only allow circular reference, e.g. Create A Timestamp In Excel With A Formula - YouTube or google "excel timestamp", lot of samples. However, that could be side effects with other calculations.