You can do it with a little event macro code:
Right click on the worksheet tab that should have this behavior. Paste this in
the code window:
Option Explicit
Private Sub Worksheet_Change(ByVal Target As Range)
Dim myRng As Range
Set myRng = Me.Range("b:b")
If Target.Cells.Count > 1 Then Exit Sub
If Intersect(Target, myRng) Is Nothing Then Exit Sub
On Error GoTo errHandler:
Application.EnableEvents = False
With Target
If .Value = "" Then
.Offset(0, -1).ClearContents
Else
With .Offset(0, -1)
.Value = Now
.NumberFormat = "mm/dd/yyyy hh:mm:ss"
End With
End If
End With
errHandler:
Application.EnableEvents = True
End Sub
I looked in column B for changes. If it got cleared, it removed the date/time
in column A. If you changed it to something, then it put the date/time in
Column A.
If you're new to macros, you may want to read David McRitchie's intro at:
http://www.mvps.org/dmcritchie/excel/getstarted.htm
