Sub ProcessAccountingReport()
    ' 1. 宣告變數 (好的習慣)
    Dim ws As Worksheet
    Dim LastRow As Long
    Dim i As Long
    
    Set ws = ThisWorkbook.Sheets("RawData")
    
    ' 2. 找出最後一列 (關鍵！因為每個月的資料筆數不同)
    LastRow = ws.Cells(ws.Rows.Count, 1).End(xlUp).Row
    
    ' 3. 新增標題欄位
    ws.Range("E1").Value = "營業稅(5%)"
    ws.Range("F1").Value = "含稅總額"
    
    ' 4. 迴圈計算 (從第2列算到最後一列)
    For i = 2 To LastRow
        ' 計算營業稅 (D欄 * 0.05)
        ws.Cells(i, 5).Value = ws.Cells(i, 4).Value * 0.05
        
        ' 計算總額 (D欄 + E欄)
        ws.Cells(i, 6).Value = ws.Cells(i, 4).Value + ws.Cells(i, 5).Value
    Next i
    
    Range("E1:F1").Select
    With Selection.Interior
        .Pattern = xlSolid
        .PatternColorIndex = xlAutomatic
        .Color = 12611584
        .TintAndShade = 0
        .PatternTintAndShade = 0
    End With
    With Selection.Font
        .ThemeColor = xlThemeColorDark1
        .TintAndShade = 0
    End With
    Selection.Font.Bold = True
    
    MsgBox "計算完成！"
End Sub