Gem imported live data, og gem den gamle data i Excel.

Option Explicit
Dim Sheet1 As Worksheet, Sheet2 As Worksheet
Dim rS1Cell As Range, rS2Cell As Range, rCell As Range

Private Sub Worksheet_Activate()
    Set Sheet1 = Sheets(1)
    Set Sheet2 = Sheets(2)
    Set rS1Cell = Sheet1.Range("A1")
    Set rS2Cell = Sheet2.Range("A1")
    If Not rS2Cell.Offset(1, 0).Value = "" Then Set rS2Cell = Range(rS2Cell, rS2Cell.End(xlDown))
    For Each rCell In rS2Cell
        If rCell.Value = rS1Cell.Value Then Exit Sub
    Next
    rS2Cell(rS2Cell.Rows.Count).Offset(1, 0) = rS1Cell
End Sub