All you need to do is select the code page for the worksheet in question, select the dropdown at the top left (which should say '(general)'), pick 'Worksheet' then select the 'Change' member of the dropdown on the right. This will give you the Event sub. For a test, write this into it
Private Sub Worksheet_Change(ByVal Target As Range)
Got to the actual sheet, type something into a cell, and hit enter. You should get a messagebox showing the affected cell. Then all you need to do is place a breakpoint in the code, and you're done.
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