耶....把DW1943建議放進去就可以了，可不知道tp34x大的方法哪個好？

Private Sub Worksheet_Change(ByVal target As Range)

Dim number As String

Application.EnableEvents = False
If Range("c" & target.Row).Value <> "" Then
number = Right(Range("c" & target.Row), 5)
Cells(target.Row, "a").Value = number

ElseIf Range("D" & target.Row).Value <> "" Then
number = Right(Range("D" & target.Row), 5)
Cells(target.Row, "a").Value = number
End If
Application.EnableEvents = True
End Sub