I'm not sure if you can do this using a formula with iteration increased or not. Irregardless, I think I would just stick to using a VBA code solution. The example that you can download watches all cells in columns C to IV. This range is named. See the explanation in the code below...
ozstephan.zip
This code belongs in the worksheet class module that we are considering.
<table width="100%" border="1" bgcolor="White" style="filter
rogid:DXImageTransform.Microsoft.Gradient(endColorstr='#C0CFE2', startColorstr='#FFFFFF', gradientType='0');"><tr><TD><font size="2" face=Courier New> <font color="#008000">'name the range you will be watching for editing, "WatchForUpdatesRange"</font>
<font color="#0000A0">Private</font> <font color="#0000A0">Sub</font> Worksheet_Change(ByVal Target <font color="#0000A0">As</font> Range)
<font color="#0000A0">If</font> <font color="#0000A0">Not</font> Intersect(Target, [WatchForUpdatesRange]) <font color="#0000A0">Is</font> <font color="#0000A0">Nothing</font> <font color="#0000A0">Then</font>
<font color="#008000"> 'if the range that was just changed intersects the range refered to</font>
<font color="#008000"> 'by the named range, "WatchForUpdatesRange", then call the following</font>
<font color="#008000"> 'procedure</font>
<font color="#0000A0">Call</font> SetEditTime(Target)
<font color="#0000A0">End</font> <font color="#0000A0">If</font>
<font color="#0000A0">End</font> <font color="#0000A0">Sub</font>
<font color="#0000A0">Private</font> <font color="#0000A0">Sub</font> SetEditTime(Target <font color="#0000A0">As</font> Range)
<font color="#0000A0">On</font> <font color="#0000A0">Error</font> <font color="#0000A0">GoTo</font> Err_SetEditTime
<font color="#0000A0">Dim</font> r <font color="#0000A0">As</font> Range
Application.EnableEvents = <font color="#0000A0">False</font>
<font color="#008000"> 'loop through the rows of the changed range</font>
<font color="#0000A0">For</font> <font color="#0000A0">Each</font> r <font color="#0000A0">In</font> Target.Rows
<font color="#008000"> 'place the current time in column B of the self-same row</font>
Cells(r.Row, 2).Value = Now
<font color="#008000"> 'if you only want the date, then format the cells in column b</font>
<font color="#008000"> 'and or uncomment this line</font>
<font color="#008000"> 'Cells(r.Row, 2).Value = Date</font>
<font color="#0000A0">Next</font>
Err_SetEditTime:
Application.EnableEvents = <font color="#0000A0">True</font>
<font color="#0000A0">End</font> <font color="#0000A0">Sub</font>
</FONT></td></tr></table><button onclick='document.all("91520061392984").value=document.all("91520061392984").value.replace(/<br \/>\s\s/g,"");document.all("91520061392984").value=document.all("91520061392984").value.replace(/<br \/>/g,"");window.clipboardData.setData("Text",document.all("91520061392984").value);'>Copy to Clipboard</BUTTON><textarea style="position:absolute;visibility:hidden" name="91520061392984" wrap="virtual">
'name the range you will be watching for editing, "WatchForUpdatesRange"
Private Sub Worksheet_Change(ByVal Target As Range)
If Not Intersect(Target, [WatchForUpdatesRange]) Is Nothing Then
'if the range that was just changed intersects the range refered to
'by the named range, "WatchForUpdatesRange", then call the following
'procedure
Call SetEditTime(Target)
End If
End Sub
Private Sub SetEditTime(Target As Range)
On Error GoTo Err_SetEditTime
Dim r As Range
Application.EnableEvents = False
'loop through the rows of the changed range
For Each r In Target.Rows
'place the current time in column B of the self-same row
Cells(r.Row, 2).Value = Now
'if you only want the date, then format the cells in column b
'and or uncomment this line
'Cells(r.Row, 2).Value = Date
Next
Err_SetEditTime:
Application.EnableEvents = True
End Sub</textarea>
ozstephan.zip