You cannot do this with a spreadsheet function, since it would recalculate each time you recalculated, resulting in the current date.
You will need to use the Worksheet_Change event.
1. Alt+F11 activates the VB editor
2. In the Project Explorer, right click the sheet object that you want the date stamp on.
3. In the Object drop down box (in the upper, L-H corner of code window) select Worksheet
4. In the Procedure window (in the upper, R-H corner of code window) select Change
5. Now code for column G changing and putting the DateStamp in column F (modify for your specific situation)
Private Sub Worksheet_Change(ByVal Target As Range) Dim Cell As Range For Each Cell In Target With Cell If .Column = Range("G:G").Column Then Cells(.Row, "F").Value = Int(Now) End If End With Next Cell End Sub