Oh, la,la, 3GB, comme tu te compliques la vie !
Une macro en 'ThisWorkbook...
Private Sub Workbook_SheetChange(ByVal Sh As Object, ByVal Target As Range)
'
If Selection.Count > 1 Then Exit Sub
Application.EnableEvents = False
Application.ScreenUpdating = False
'
If Not Intersect(Target, Sh.Columns(1)) Is Nothing Then
For x = 1 To Sheets.Count
Sheets(x).Range("A" & Target.Row).Value = Target
Next
End If
'
Application.ScreenUpdating = True
Application.EnableEvents = True
'
End Sub
A+