You want to capture that instant in date/time when the values in column C
become non-blank. You need an event macro to do that:
Private Sub Worksheet_Change(ByVal Target As Range)
If Not Intersect(Range("C4:C94"), Target) Is Nothing Then
Application.EnableEvents = False
Target.Offset(0, 1).Value = Now()
Application.EnableEvents = True
End If
End Sub
format column D as you prefer.
Because it is worksheet code, it is very easy to install and use:
1. right-click the tab name near the bottom of the window
2. select View Code - this brings up a VBE window
3. paste the stuff in and close the VBE window
Now try entering material in column C. If you have any concerns, first try
it on a trial worksheet.
If you save the workbook, the macro will be saved with it.
To remove the macro:
1. bring up the VBE windows as above
2. clear the code out
3. close the VBE window
To learn more about macros in general, see:
http://www.mvps.org/dmcritchie/excel/getstarted.htm
To learn more about Event Macros (worksheet code), see:
http://www.mvps.org/dmcritchie/excel/event.htm