Auto insert a Static date

[AJW77]

I was wondering if there is a way to automatically insert the static date in a worksheet if value is entered in another cell.

Example/reason.

I have a UAT testing log, and when the customer selects ‘Complete’ from a dropdown, (in cell I4), then I want the static date to be populated into another cell (O4) to show and record the date the action was completed.

Any advice most welcome.

Much Obliged

[#2]

@AJW77 

To my knowledge there are two ways - use some VBA programming; or formula like this

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

but the latest requires that iterative calculations to be swithed on

what could have a negative side effect.