Put this event macro in the worksheet code area of the first tab:
Private Sub Worksheet_Change(ByVal Target As Range)
Dim s1 As Worksheet, s2 As Worksheet
Set s1 = Sheets("Sheet1")
Set s2 = Sheets("Sheet2")
Set t = Target
If Intersect(t, Range("M:M")) Is Nothing Then Exit Sub
n = s2.Cells(Rows.Count, "M").End(xlUp).Row + 1
Application.EnableEvents = False
t.EntireRow.Copy s2.Range("A" & n)
Application.EnableEvents = True
End Sub
Naturally you need to make changes to match your tab names.
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
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